0000017313-23-000082 | 10-Q | XBRL Viewer

INCOME TAXES (Tables)

3 Months Ended

Jun. 30, 2023

Schedule of Net Assets Resulting from Operations to Estimated RIC Taxable Income

The following reconciles net increase in net assets resulting from operations to estimated RIC taxable income for the three months ended June 30, 2023 and 2022:


	Three Months Ended June 30,
Reconciliation of RIC Distributable Income1	2023		2022
Net increase in net assets from operations	$	23,812	$	2,510
Net unrealized depreciation (appreciation) on investments	(12,038)		12,248
(Expense/loss) income/gain recognized for tax on pass-through entities	(4,202)		40
(Gain) loss recognized on dispositions	(1,641)		—
Capital loss carryover2	17,932		(1,567)
Net operating income - wholly-owned subsidiary	(1,796)		(1,534)
Dividend income from wholly-owned subsidiary	—		907
Non-deductible tax expense	93		73
Loss on extinguishment of debt	(682)		(682)
Non-deductible compensation	892		822
Compensation related book/tax differences	(5,824)		(5,529)
Interest on non-accrual loans	1,415		1,128
Other book/tax differences	1,610		257
Estimated distributable income before deductions for distributions	$	19,571	$	8,673

1The calculation of taxable income for each period is an estimate and will not be finally determined until the Company files its tax return each year. Final taxable income may be different than this estimate.

2At June 30, 2023, the Company had long-term capital loss carryforwards of $49.1 million to offset future capital gains. These capital loss carryforwards are not subject to expiration.

Schedule of Deferred Tax Assets and Liabilities

The following table sets forth the significant components of the deferred tax assets and liabilities as of June 30, 2023 and March 31, 2023 (amounts in thousands):


	June 30, 2023		March 31, 2023
Deferred tax asset:
Net operating loss carryforwards	$	—	$	—
Interest	276		219
Total deferred tax asset	276		219
Deferred tax liabilities:
Net unrealized appreciation on investments	(11,433)		(11,413)
Net basis differences in portfolio investments	(698)		(923)
Total deferred tax liabilities	(12,131)		(12,336)
Total net deferred tax (liabilities) assets	$	(11,855)	$	(12,117)

BORROWINGS

3 Months Ended

Jun. 30, 2023

Debt Disclosure [Abstract]

BORROWINGS

In accordance with the 1940 Act, effective April 25, 2019, the Company is only allowed to borrow amounts such that its asset coverage (i.e., the ratio of assets less liabilities not represented by senior securities to senior securities such as borrowings), calculated pursuant to the 1940 Act, is at least 150% after such borrowing. The Board of Directors also approved a resolution that limits the Company’s issuance of senior securities such that the asset coverage ratio, taking into account any such issuance, would not be less than 166%, which became effective April 25, 2019. On August 11, 2021, we received an exemptive order from SEC to permit us to exclude the senior securities issued by SBIC I or any future SBIC subsidiary of the Company from the definition of senior securities in the asset coverage requirement applicable to the Company under the 1940 Act. As of June 30, 2023, the Company’s asset coverage was 237%.

The Company had the following borrowings outstanding as of June 30, 2023 and March 31, 2023 (amounts in thousands):


	Outstanding Balance		Unamortized Debt Issuance Costs and Debt Discount/Premium(1)		Recorded Value
June 30, 2023
SBA Debentures	$	125,000	$	(3,648)	$	121,352
Credit Facility	195,000		—		195,000
January 2026 Notes	140,000		(865)		139,135
October 2026 Notes	150,000		(2,552)		147,448
August 2028 Notes	71,875		(2,548)		69,327
	$	681,875	$	(9,613)	$	672,262

March 31, 2023
SBA Debentures	$	120,000	$	(3,670)	$	116,330
Credit Facility	235,000		—		235,000
January 2026 Notes	140,000		(949)		139,051
October 2026 Notes	150,000		(2,737)		147,263
	$	645,000	$	(7,356)	$	637,644

(1)The unamortized debt issuance costs for the Credit Facility are reflected as Debt issuance costs on the Consolidated Statements of Assets and Liabilities.

Credit Facility

In August 2016, CSWC entered into a senior secured revolving credit facility (the “Credit Facility”) to provide additional liquidity to support its investment and operational activities.

On August 9, 2021, CSWC entered into the Second Amended and Restated Senior Secured Revolving Credit Agreement (as amended or otherwise modified from time to time, the "Credit Agreement"). Prior to the Credit Agreement, (1) borrowings under the Credit Facility accrued interest on a per annum basis at a rate equal to the applicable LIBOR rate plus 2.50% with no LIBOR floor, and (2) the total borrowing capacity was $340 million with commitments from a diversified group of eleven lenders. The Credit Agreement (1) decreased the total borrowing capacity under the Credit Facility to $335 million with commitments from a diversified group of ten lenders, (2) reduced the interest rate on borrowings to LIBOR plus 2.15% with no LIBOR floor and removed conditions related thereto as previously set forth in the Amended and Restated Senior Secured Revolving Credit Agreement, and (3) extended the end of the Credit Facility's revolver period from December 21, 2022 to August 9, 2025 and extended the final maturity from December 21, 2023 to August 9, 2026. The Credit Agreement also modified certain covenants in the Credit Facility, including, among other things, to increase the minimum obligors’ net worth test from $180 million to $200 million.

entered into an Incremental Commitment Agreement, pursuant to which the total commitments under the Credit Agreement increased from $335 million to $380 million. On November 16, 2022, CSWC entered into an Incremental Assumption Agreement that increased the total commitments of the Credit Agreement by $20 million, which increased total commitments from $380 million to $400 million. The $20 million increase was provided by one existing lender and one new lender, bringing the total bank syndicate to eleven participants.

CSWC pays unused commitment fees of 0.50% to 1.00% per annum, based on utilization, on the unused lender commitments under the Credit Facility. The Credit Facility contains certain affirmative and negative covenants, including but not limited to: (1) certain reporting requirements, (2) maintaining RIC and BDC status, (3) maintaining a minimum senior coverage ratio of 2 to 1, (4) maintaining a minimum shareholders’ equity, (5) maintaining a minimum consolidated net worth, (6) maintaining a regulatory asset coverage of not less than 150%, (7) maintaining an interest coverage ratio of at least 2.25 to 1.0, and (8) at any time the outstanding advances exceed 90% of the borrowing base, maintaining a minimum liquidity of not less than 10% of the covered debt amount.

The Credit Agreement also contains customary events of default, including, without limitation, nonpayment, misrepresentation of representations and warranties in a material respect, breach of covenant, bankruptcy, and change of control, with customary cure and notice provisions. If the Company defaults on its obligations under the Credit Agreement, the lenders may have the right to foreclose upon and sell, or otherwise transfer, the collateral subject to their security interests.

The Credit Facility is secured by (1) substantially all of the present and future property and assets of the Company and the guarantors and (2) 100% of the equity interests in the Company’s wholly-owned subsidiary. As of June 30, 2023, substantially all of the Company’s assets were pledged as collateral for the Credit Facility, except for assets held in SBIC I.

At June 30, 2023, CSWC had $195.0 million in borrowings outstanding under the Credit Facility. CSWC recognized interest expense related to the Credit Facility, including unused commitment fees and amortization of deferred loan costs, of $4.9 million and $1.9 million for the three months ended June 30, 2023 and 2022, respectively. The weighted average interest rate on the Credit Facility was 7.36% and 3.16% for the three months ended June 30, 2023 and 2022, respectively. Average borrowings for the three months ended June 30, 2023 and 2022 were $239.7 million and $182.9 million, respectively. As of June 30, 2023 and 2022, CSWC was in compliance with all financial covenants under the Credit Agreement.

January 2026 Notes

In December 2020, the Company issued $75.0 million in aggregate principal amount of 4.50% Notes due 2026 (the "Existing January 2026 Notes"). The Existing January 2026 Notes were issued at par. In February 2021, the Company issued an additional $65.0 million in aggregate principal amount of the January 2026 Notes (the "Additional January 2026 Notes" together with the Existing January 2026 Notes, the "January 2026 Notes"). The Additional January 2026 Notes were issued at a price of 102.11% of the aggregate principal amount of the Additional January 2026 Notes, resulting in a yield-to-maturity of approximately 4.0% at issuance. The Additional January 2026 Notes are treated as a single series with the Existing January 2026 Notes under the indenture and have the same terms as the Existing January 2026 Notes. The January 2026 Notes mature on January 31, 2026 and may be redeemed in whole or in part at any time prior to October 31, 2025, at par plus a "make-whole" premium, and thereafter at par. The January 2026 Notes bear interest at a rate of 4.50% per year, payable semi-annually on January 31 and July 31 of each year. The January 2026 Notes are the direct unsecured obligations of the Company, rank pari passu with the Company's other outstanding and future unsecured unsubordinated indebtedness and are effectively or structurally subordinated to all of the Company's existing and future secured indebtedness, including borrowings under the Credit Facility and the SBA Debentures.

As of June 30, 2023, the carrying amount of the January 2026 Notes was $139.1 million on an aggregate principal amount of $140.0 million at a weighted average effective yield of 4.46%. As of June 30, 2023, the fair value of the January 2026 Notes was $118.4 million. This is a Level 3 fair value measurement under ASC 820 based on a valuation model using a discounted cash flow analysis. The Company recognized interest expense related to the January 2026 Notes, including amortization of deferred issuance costs, of $1.7 million for each of the three months ended June 30, 2023 and 2022. For each of the three months ended June 30, 2023 and 2022, average borrowings were $140.0 million.

subject to certain other exceptions, and to provide financial information to the holders of the January 2026 Notes and the trustee under the indenture if the Company is no longer subject to the reporting requirements under the Securities Exchange Act of 1934, as amended (the "Exchange Act"). These covenants are subject to important limitations and exceptions that are described in the indenture and the third supplemental indenture relating to the January 2026 Notes.

In addition, holders of the January 2026 Notes can require the Company to repurchase some or all of the January 2026 Notes at a purchase price equal to 100% of their principal amount, plus accrued and unpaid interest to, but not including, the repurchase date upon the occurrence of a “Change of Control Repurchase Event,” as defined in the third supplemental indenture relating to the January 2026 Notes.

October 2026 Notes

As of June 30, 2023, the carrying amount of the October 2026 Notes was $147.4 million on an aggregate principal amount of $150.0 million at a weighted average effective yield of 3.5%. As of June 30, 2023, the fair value of the October 2026 Notes was $127.8 million. This is a Level 3 fair value measurement under ASC 820 based on a valuation model using a discounted cash flow analysis. The Company recognized interest expense related to the October 2026 Notes, including amortization of deferred issuance costs, of $1.5 million and $1.4 million for the three months ended June 30, 2023 and 2022, respectively. For each of the three months ended June 30, 2023 and 2022, average borrowings were $150.0 million.

The indenture governing the October 2026 Notes contains certain covenants, including certain covenants requiring the Company to comply with Section 18(a)(1)(A) as modified by Section 61(a)(2) of the 1940 Act, or any successor provisions, whether or not the Company continues to be subject to such provisions of the 1940 Act, but giving effect, in either case, to any exemptive relief granted to the Company by the SEC, to comply with Section 18(a)(1)(B) as modified by Section 61(a)(2) of the 1940 Act, or any successor provisions, after giving effect to any exemptive relief granted to the Company by the SEC and subject to certain other exceptions, and to provide financial information to the holders of the October 2026 Notes and the trustee under the indenture if the Company is no longer subject to the reporting requirements under the Exchange Act. These covenants are subject to important limitations and exceptions that are described in the indenture and the fourth supplemental indenture relating to the October 2026 Notes.

In addition, holders of the October 2026 Notes can require the Company to repurchase some or all of the October 2026 Notes at a purchase price equal to 100% of their principal amount, plus accrued and unpaid interest to, but not including, the repurchase date upon the occurrence of a “Change of Control Repurchase Event,” as defined in the fourth supplemental indenture relating to the October 2026 Notes.

August 2028 Notes

In June 2023, the Company issued approximately $71.9 million in aggregate principal amount, including the underwriters' full exercise of their option to purchase an additional $9.4 million in aggregate principal amount to cover over-allotments, of 7.75% notes due 2028 (the "August 2028 Notes"). The August 2028 Notes mature on August 1, 2028 and may be redeemed in whole or in part at any time, or from time to time, at the Company’s option on or after August 1, 2025. The August 2028 Notes bear interest at a rate of 7.75% per year, payable quarterly on February 1, May 1, August 1 and November 1 of each year, beginning on August 1, 2023. The August 2028 Notes are the direct unsecured obligations of the Company, rank pari passu with the Company's other outstanding and future unsecured unsubordinated indebtedness and are effectively or structurally subordinated to all of the Company's existing and future secured indebtedness, including borrowings under the

Credit Facility and the SBA Debentures. The August 2028 Notes are listed on the Nasdaq Global Select Market under the trading symbol "CSWCZ."

As of June 30, 2023, the carrying amount of the August 2028 Notes was $69.3 million on an aggregate principal amount of $71.9 million at a weighted average effective yield of 7.75%. As of June 30, 2023, the fair value of the August 2028 Notes was $72.3 million. The fair value is based on the closing price of the security on The Nasdaq Global Select Market, which is a Level 1 input under ASC 820. The Company recognized interest expense related to the August 2028 Notes, including amortization of deferred issuance costs, of $0.3 million for the three months ended June 30, 2023. Since the issuance of the August 2028 Notes on June 14, 2023 through June 30, 2023, average borrowings were $71.9 million.

The indenture governing the August 2028 Notes contains certain covenants, including certain covenants requiring the Company to comply with Section 18(a)(1)(A) as modified by Section 61(a)(2) of the 1940 Act, or any successor provisions, whether or not the Company continues to be subject to such provisions of the 1940 Act, but giving effect, in either case, to any exemptive relief granted to the Company by the SEC, to comply with Section 18(a)(1)(B) as modified by Section 61(a)(2) of the 1940 Act, or any successor provisions, after giving effect to any exemptive relief granted to the Company by the SEC and subject to certain other exceptions, and to provide financial information to the holders of the August 2028 Notes and the trustee under the indenture if the Company is no longer subject to the reporting requirements under the Exchange Act. These covenants are subject to important limitations and exceptions that are described in the indenture and the fifth supplemental indenture relating to the August 2028 Notes.

SBA Debentures

On April 20, 2021, SBIC I received a license from the SBA to operate as an SBIC under Section 301(c) of the Small Business Investment Act of 1958, as amended. The license allows SBIC I to obtain leverage by issuing SBA Debentures, subject to the issuance of a leverage commitment by the SBA. SBA Debentures are loans issued to an SBIC which have interest payable semi-annually and a ten-year maturity. The interest rate is fixed shortly after issuance at a market-driven spread over U.S. Treasury Notes with ten-year maturities. Interest on SBA Debentures is payable semi-annually on March 1 and September 1. Current statutes and regulations permit SBIC I to borrow up to $175 million in SBA Debentures with at least $87.5 million in regulatory capital (as defined in the SBA regulations).

On May 25, 2021, SBIC I received a leverage commitment from the SBA in the amount of $40.0 million to be issued on or prior to September 30, 2025. On January 28, 2022, SBIC I received an additional leverage commitment in the amount of $40.0 million to be issued on or prior to September 30, 2026. On November 22, 2022, SBIC I received an additional leverage commitment in the amount of $50.0 million to be issued on or prior to September 30, 2027. As of June 30, 2023, SBIC I had regulatory capital of $65.0 million and leverageable capital of $65.0 million. As of June 30, 2023, SBIC I had a total leverage commitment from the SBA in the amount of $130.0 million, of which $5.0 million remains unused. The SBA may limit the amount that may be drawn each year under these commitments, and each issuance of leverage is conditioned on the Company’s full compliance, as determined by the SBA, with the terms and conditions set forth in the SBA regulations.

As of June 30, 2023, the carrying amount of SBA Debentures was $121.4 million on an aggregate principal amount of $125.0 million. As of June 30, 2023, the fair value of the SBA Debentures was $117.8 million. The fair value of the SBA Debentures is estimated by discounting the remaining payments using current market rates for similar instruments and considering such factors as the legal maturity date and the ability of market participants to prepay the SBA Debentures, which are Level 3 inputs under ASC 820. The Company recognized interest expense and fees related to SBA Debentures of $1.4 million and $0.4 million for the three months ended June 30, 2023 and 2022, respectively. The weighted average interest rate on the SBA Debentures was 3.94% and 2.50% for the three months ended June 30, 2023 and 2022, respectively. For the three months ended June 30, 2023 and 2022, average borrowings were $123.7 million and $51.6 million, respectively.

As of June 30, 2023, the Company's issued and outstanding SBA Debentures mature as follows (amounts in thousands):


Pooling Date (1)	Maturity Date	Fixed Interest Rate	June 30, 2023
9/22/2021	9/1/2031	1.575%	$	15,000
3/23/2022	3/1/2032	3.209%	25,000
9/21/2022	9/1/2032	4.435%	40,000
3/22/2023	3/1/2033	5.215%	40,000
(2)	(2)	(2)	5,000
			$	125,000

(1)The SBA has two scheduled pooling dates for SBA Debentures (in March and in September). Certain SBA Debentures funded during the reporting periods may not be pooled until the subsequent pooling date.

(2)The Company issued $5.0 million in SBA Debentures that will pool in September 2023. Until the pooling date, the SBA Debentures bear interest at a fixed rate with a weighted-average interim interest rate of 5.66%.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480678/235-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 470
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//470/tableOfContent

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1B

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1C

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1E

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481139/470-20-50-1I

+ Details

CONSOLIDATED SCHEDULE OF INVESTMENTS - USD ($)
$ in Thousands

Jun. 30, 2023

Mar. 31, 2023

OTHER EMPLOYEE COMPENSATION (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Retirement Benefits [Abstract]
Employer matching contribution (up to)	4.50%
Matching contributions cost	$ 0.1	$ 0.1

COMMITMENTS AND CONTINGENCIES - Future Minimum Payments (Details) $ in Thousands	Jun. 30, 2023 USD ($)
Commitments and Contingencies Disclosure [Abstract]
2024	$ 306
2025	416
2026	426
2027	436
2028	446
Thereafter	2,132
Total	$ 4,162

ORGANIZATION AND BASIS OF PRESENTATION (Details)	3 Months Ended
ORGANIZATION AND BASIS OF PRESENTATION (Details)	Jun. 30, 2023 USD ($)
Schedule of Investments [Line Items]
Qualifying assets	85.20%
Nonqualified assets	11.00%
LMM \| Minimum
Schedule of Investments [Line Items]
Target company, annual EBITDA	$ 3,000,000
Target investment	5,000,000
LMM \| Maximum
Schedule of Investments [Line Items]
Target company, annual EBITDA	20,000,000
Target investment	35,000,000
UMM \| Minimum
Schedule of Investments [Line Items]
Target company, annual EBITDA	20,000,000
Target investment	5,000,000
UMM \| Maximum
Schedule of Investments [Line Items]
Target investment	$ 20,000,000

SUBSEQUENT EVENTS	3 Months Ended
SUBSEQUENT EVENTS	Jun. 30, 2023
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS On August 2, 2023, the Company entered into the Third Amended and Restated Senior Secured Revolving Credit Agreement, which (1) increased commitments under the Credit Facility from $400 million to $435 million; (2) added an uncommitted accordion feature that could increase the maximum commitments up to $750 million; (3) extended the end of the Credit Facility's revolving period from August 9, 2025 to August 2, 2027 and extended the final maturity from August 9, 2026 to August 2, 2028; and (4) amended several financial covenants. On August 3, 2023, the Board of Directors declared a total dividend of $0.62 per share, comprised of a regular dividend of $0.56 and a supplemental dividend of $0.06, for the quarter ending September 30, 2023. The record date for the dividend is September 15, 2023. The payment date for the dividend is September 29, 2023.

INCOME TAXES - Deferred Tax Assets And Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Mar. 31, 2023
Deferred tax asset:
Net operating loss carryforwards	$ 0	$ 0
Interest	276	219
Total deferred tax asset	276	219
Deferred tax liabilities:
Net unrealized appreciation on investments	(11,433)	(11,413)
Net basis differences in portfolio investments	(698)	(923)
Total deferred tax liabilities	(12,131)	(12,336)
Total net deferred tax (liabilities) assets	$ (11,855)	$ (12,117)

BORROWINGS - Schedule of Issued and Outstanding SBA Debentures (Details) $ in Thousands	3 Months Ended
	Jun. 30, 2023 USD ($) poolingDate	Jun. 30, 2022	Mar. 31, 2023 USD ($)
Debt Instrument [Line Items]
Outstanding Balance	$ 681,875		$ 645,000
Unsecured Debt \| SBA Debentures
Debt Instrument [Line Items]
Outstanding Balance	$ 125,000		$ 120,000
Number of pooling date \| poolingDate	2
Weighted-average interest rate	3.94%	2.50%
Unsecured Debt \| Debentures due September 2031
Debt Instrument [Line Items]
Fixed Interest Rate	1.575%
Outstanding Balance	$ 15,000
Unsecured Debt \| Debentures due March 2032
Debt Instrument [Line Items]
Fixed Interest Rate	3.209%
Outstanding Balance	$ 25,000
Unsecured Debt \| Debentures due September 2032
Debt Instrument [Line Items]
Fixed Interest Rate	4.435%
Outstanding Balance	$ 40,000
Unsecured Debt \| Debentures due March 2033
Debt Instrument [Line Items]
Fixed Interest Rate	5.215%
Outstanding Balance	$ 40,000
Unsecured Debt \| Debentures not pooled
Debt Instrument [Line Items]
Outstanding Balance	$ 5,000
Weighted-average interest rate	5.66%

ORGANIZATION AND BASIS OF PRESENTATION	3 Months Ended
ORGANIZATION AND BASIS OF PRESENTATION	Jun. 30, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION AND BASIS OF PRESENTATION	ORGANIZATION AND BASIS OF PRESENTATION References in this Quarterly Report on Form 10-Q to “we,” “our,” “us,” “CSWC,” or the “Company” refer to Capital Southwest Corporation, unless the context requires otherwise. Organization Capital Southwest Corporation is an internally managed investment company that specializes in providing customized financing to middle market companies in a broad range of investment segments located primarily in the United States. CSWC has elected to be regulated as a business development company under the 1940 Act. Our common stock currently trades on The Nasdaq Global Select Market under the ticker symbol “CSWC.” We have elected, and intend to qualify annually, to be treated for U.S. federal income tax purposes as a regulated investment company (“RIC”) under Subchapter M of the U.S. Internal Revenue Code of 1986, as amended (the “Code”). As such, we generally will not have to pay U.S. federal income tax at corporate rates on any ordinary income or capital gains that we distribute to our shareholders as dividends. To continue to maintain our RIC tax treatment, we must meet specified source-of-income and asset diversification requirements and timely distribute annually at least 90% of our net ordinary income and realized net short-term capital gains in excess of realized net long-term capital losses, if any. We may be subject to U.S. federal income tax and a 4% U.S. federal excise tax on any income that we do not timely distribute to our shareholders. Our U.S. federal income tax liability may be reduced to the extent that we make certain distributions during the following calendar year and satisfy other procedural requirements. We focus on investing in companies with histories of generating revenues and positive cash flow, established market positions and proven management teams with strong operating discipline. Our core business is to target senior debt investments and equity investments in lower middle market (“LMM”) companies. We also opportunistically target first and second lien loans in upper middle market (“UMM”) companies. Our target LMM companies typically have annual earnings before interest, taxes, depreciation and amortization (“EBITDA”) generally between $3.0 million and $20.0 million, and our LMM investments generally range in size from $5.0 million to $35.0 million. Our UMM investments generally include first and second lien loans in companies with EBITDA generally greater than $20.0 million and typically range in size from $5.0 million to $20.0 million. We make available significant managerial assistance to the companies in which we invest as we believe that providing managerial assistance to an investee company is critical to its business development activities. CSWC has a direct wholly-owned subsidiary that has been elected to be a taxable entity (the “Taxable Subsidiary”). The primary purpose of the Taxable Subsidiary is to permit CSWC to hold certain interests in portfolio companies that are organized as limited liability companies, or LLCs (or other forms of pass-through entities), and still allow us to satisfy the RIC tax requirement that at least 90% of our gross income for U.S. federal income tax purposes must consist of qualifying investment income. The Taxable Subsidiary is taxed at normal corporate tax rates based on its taxable income. On April 20, 2021, our wholly owned subsidiary, Capital Southwest SBIC I, LP (“SBIC I”), received a license from the U.S. Small Business Administration (the “SBA”) to operate as a small business investment company ("SBIC") under Section 301(c) of the Small Business Investment Act of 1958, as amended. SBIC I has an investment strategy substantially similar to ours and makes similar types of investments in accordance with SBA regulations. SBIC I and its general partner are consolidated for financial reporting purposes under generally accepted accounting principles in the United States ("U.S. GAAP"), and the portfolio investments held by it are included in the consolidated financial statements. Basis of Presentation The consolidated financial statements have been prepared in accordance with U.S. GAAP. We meet the definition of an investment company and follow the accounting and reporting guidance in the Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 946, Financial Services – Investment Companies (“ASC 946”). Under rules and regulations applicable to investment companies, we are generally precluded from consolidating any entity other than another investment company, subject to certain exceptions. One of the exceptions to this general principle occurs if the investment company has an investment in an operating company that provides services to the investment company. Accordingly, the consolidated financial statements include the Taxable Subsidiary and SBIC I. Portfolio Investment Classification We classify our investments in accordance with the requirements of the 1940 Act. Under the 1940 Act, “Control Investments” are generally defined as investments in which we own more than 25% of the voting securities; “Affiliate Investments” are generally defined as investments in which we own between 5% and 25% of the voting securities, and the investments are not classified as “Control Investments”; and “Non-Control/Non-Affiliate Investments” are generally defined as investments that are neither “Control Investments” nor “Affiliate Investments.” Under the 1940 Act, a BDC must meet certain requirements, including investing at least 70% of its total assets in qualifying assets. As of June 30, 2023, the Company has 85.2% of its total assets (at fair value) in qualifying assets. The principal categories of qualifying assets relevant to our business are: (1)securities purchased in transactions not involving any public offering from the issuer of such securities, which issuer (subject to certain limited exceptions) is an "eligible portfolio company," or from any person who is, or has been during the preceding 13 months, an affiliated person of an eligible portfolio company, or from any other person, subject to such rules as may be prescribed by the Securities and Exchange Commission ("SEC"); (2)securities of any eligible portfolio company that we control; (3)securities purchased in a private transaction from a U.S. issuer that is not an investment company or from an affiliated person of the issuer, or in transactions incident thereto, if the issuer is in bankruptcy and subject to reorganization or if the issuer, immediately prior to the purchase of its securities was unable to meet its obligations as they came due without material assistance other than conventional lending or financing arrangements; (4)securities of an eligible portfolio company purchased from any person in a private transaction if there is no readily available market for such securities and we already own 60% of the outstanding equity of the eligible portfolio company; (5)securities received in exchange for or distributed on or with respect to securities described in (1) through (4) above, or pursuant to the exercise of warrants or rights relating to such securities; and (6)cash, cash equivalents, U.S. government securities or high-quality debt securities maturing in one year or less from the time of investment. Additionally, in order to qualify for RIC tax treatment for U.S. federal income tax purposes, we must, among other things meet the following requirements: (1) continue to maintain our election as a BDC under the 1940 Act at all times during each taxable year; (2) derive in each taxable year at least 90% of our gross income from dividends, interest, payments with respect to certain securities, loans, gains from the sale of stock or other securities, net income from certain "qualified publicly traded partnerships," or other income derived with respect to our business of investing in such stock or securities; and (3) diversify our holdings in accordance with two diversification requirements: (a) diversify our holdings such that at the end of each quarter of the taxable year at least 50% of the value of our assets consists of cash, cash equivalents, U.S. Government securities, securities of other RICs, and such other securities if such other securities of any one issuer do not represent more than 5% of the value of our assets or more than 10% of the outstanding voting securities of the issuer; and (b) diversify our holdings such that no more than 25% of the value of our assets is invested in the securities, other than U.S. government securities or securities of other RICs, (i) of one issuer, (ii) of two or more issuers that are controlled, as determined under applicable Code rules, by us and that are engaged in the same or similar or related trades or businesses or (iii) of certain "qualified publicly traded partnerships" (collectively, the "Diversification Requirements"); The two Diversification Requirements must be satisfied quarterly. If a RIC satisfies the Diversification Requirements for one quarter, and then, due solely to fluctuations in market value, fails to meet one of the Diversification Requirements in the next quarter, it retains RIC tax treatment. A RIC that fails to meet the Diversification Requirements as a result of a nonqualified acquisition may be subject to excess taxes unless the nonqualified acquisition is disposed of and the Diversification Requirements are satisfied within 30 days of the close of the quarter in which the Diversification Requirements are failed. For the quarter ended June 30, 2023, we satisfied all RIC requirements and have 11.0% in nonqualified assets according to measurement criteria established in Section 851(d) of the Code.

SHAREHOLDERS' EQUITY - Shares Repurchased In Connection With The Vesting Of Restricted Stock Awards (Details) - Shares repurchased for restricted stock awards vested - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Equity, Class of Treasury Stock [Line Items]
Cancellation of treasury stock (in shares)	46,581	29,673
Cancellation of treasury stock	$ 924,955	$ 641
Weighted average price per share (in usd per share)	$ 19.86	$ 21.60

RELATED PARTY TRANSACTIONS (Details) - Corporate Joint Venture - USD ($)	3 Months Ended
	Jun. 30, 2023	Mar. 31, 2023
Related Party Transaction [Line Items]
Dividends receivable	$ 2,100,000	$ 1,900,000
Management fees from our portfolio companies	$ 24,500

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Cash flows from operating activities
Net increase in net assets from operations	$ 23,812	$ 2,510
Adjustments to reconcile net increase in net assets from operations to net cash used in operating activities:
Purchases and originations of investments	(104,106)	(134,956)
Proceeds from sales and repayments of debt investments in portfolio companies	24,653	54,921
Proceeds from sales and return of capital of equity investments in portfolio companies	3,402	1,743
Payment of accreted original issue discounts	223	1,087
Depreciation and amortization	779	651
Net pension benefit	(16)	(31)
Realized loss (gain) on investments before income tax	12,461	(2,392)
Net unrealized (appreciation) depreciation on investments before income tax	(12,058)	11,167
Accretion of discounts on investments	(1,172)	(848)
Payment-in-kind interest	(1,999)	(810)
Share-based compensation expense	963	821
Deferred income taxes	(262)	1,201
Changes in other assets and liabilities:
(Increase) decrease in dividend and interest receivable	(1,647)	154
(Increase) decrease in escrow receivables	(105)	(17)
Decrease in tax receivable	266	0
Increase in other receivables	(171)	(2,090)
Decrease (increase) in other assets	260	(301)
Increase (decrease) in taxes payable	721	(1,083)
Decrease in other liabilities	(1,630)	(1,530)
Net cash used in operating activities	(55,626)	(69,803)
Cash flows from investing activities
Acquisition of fixed assets	(2)	(156)
Net cash used in investing activities	(2)	(156)
Cash flows from financing activities
Proceeds from common stock offering	44,888	46,051
Borrowings under credit facility	75,000	55,000
Repayments of credit facility	(115,000)	(45,000)
Debt issuance costs paid	(322)	(523)
Proceeds from issuance of SBA Debentures	4,878	39,026
Proceeds from issuance of August 2028 Notes	69,719	0
Dividends to shareholders	(22,916)	(16,615)
Common stock withheld for payroll taxes upon vesting of restricted stock	(926)	(641)
Net cash provided by financing activities	55,321	77,298
Net (decrease) increase in cash and cash equivalents	(307)	7,339
Cash and cash equivalents at beginning of period	21,585	11,431
Cash and cash equivalents at end of period	21,278	18,770
Supplemental cash flow disclosures:
Cash paid for income taxes	65	1,400
Cash paid for interest	$ 5,975	$ 4,520

OTHER EMPLOYEE COMPENSATION	3 Months Ended
OTHER EMPLOYEE COMPENSATION	Jun. 30, 2023
Retirement Benefits [Abstract]
OTHER EMPLOYEE COMPENSATION	OTHER EMPLOYEE COMPENSATIONWe established a 401(k) plan (the “401K Plan”) effective October 1, 2015. All full-time employees are eligible to participate in the 401K Plan. The 401K Plan permits employees to defer a portion of their total annual compensation up to the Internal Revenue Service annual maximum based on age and eligibility. We made contributions to the 401K Plan of up to 4.5% of the Internal Revenue Service’s annual maximum eligible compensation, all of which is fully vested immediately. During each of the three months ended June 30, 2023 and 2022, we made matching contributions of approximately $0.1 million.

STOCK BASED COMPENSATION PLANS - Summary of Restricted Stock Outstanding (Details) - Restricted Stock - $ / shares	3 Months Ended	12 Months Ended
	Jun. 30, 2023	Mar. 31, 2023
2010 Plan and 2021 Employee Plan
Number of Shares
Beginning balance (in shares)	432,711
Granted (in shares)	284,407
Vested (in shares)	(139,386)
Forfeited (in shares)	(1,791)
Ending balance (in shares)	575,941	432,711
Weighted Average Fair Value Per Share at grant date
Beginning balance (in dollars per share)	$ 21.61
Granted (in dollars per share)	19.86
Vested (in dollars per share)	20.91
Forfeited (in dollars per share)	23.91
Ending balance (in dollars per share)	$ 20.91	$ 21.61
Weighted Average Remaining Vesting Term (in Years)
Weighted Average Vesting Term	3 years 1 month 6 days	2 years 4 months 24 days
Non-Employee Director Plan
Number of Shares
Beginning balance (in shares)	12,105
Granted (in shares)	0
Vested (in shares)	0
Forfeited (in shares)	0
Ending balance (in shares)	12,105	12,105
Weighted Average Fair Value Per Share at grant date
Beginning balance (in dollars per share)	$ 20.66
Granted (in dollars per share)	0
Vested (in dollars per share)	0
Forfeited (in dollars per share)	0
Ending balance (in dollars per share)	$ 20.66	$ 20.66
Weighted Average Remaining Vesting Term (in Years)
Weighted Average Vesting Term	1 month 6 days

COMMITMENTS AND CONTINGENCIES - Unfunded Debt Commitments (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Mar. 31, 2023
Gain Contingencies [Line Items]
Total Unfunded Debt Commitments	$ 129,934	$ 124,637
2024
Gain Contingencies [Line Items]
Total Unfunded Debt Commitments	16,353	31,625
2025
Gain Contingencies [Line Items]
Total Unfunded Debt Commitments	10,912	10,637
2026
Gain Contingencies [Line Items]
Total Unfunded Debt Commitments	9,615	6,712
2027
Gain Contingencies [Line Items]
Total Unfunded Debt Commitments	38,925	38,062
2028
Gain Contingencies [Line Items]
Total Unfunded Debt Commitments	41,290	35,318
2029
Gain Contingencies [Line Items]
Total Unfunded Debt Commitments	$ 12,839	$ 2,283

FAIR VALUE MEASUREMENTS - Narrative (Details)	Jun. 30, 2023	Mar. 31, 2023
Privately held debt and equity instruments
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Percent of investment assets	100.00%	100.00%

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Fee income:
Other income	$ 57	$ 2
Total investment income	40,361	22,543
Compensation	2,510	1,542
Share-based compensation	963	821
Interest	9,681	5,484
Professional fees	955	849
General and administrative	1,249	1,217
Total operating expenses	15,358	9,913
Income before taxes	25,003	12,630
Federal income, excise and other taxes	599	73
Deferred taxes	(152)	119
Total income tax provision	447	192
Net investment income	24,556	12,438
Realized (loss) gain
Income tax provision	(321)	(244)
Total net realized (loss) gain on investments, net of tax	(12,782)	2,320
Net unrealized appreciation (depreciation) on investments
Income tax provision	(20)	(1,081)
Total net unrealized appreciation (depreciation) on investments, net of tax	12,038	(12,248)
Net realized and unrealized (losses) gains on investments	(744)	(9,928)
Net increase in net assets from operations	$ 23,812	$ 2,510
Pre-tax net investment income per share - basic (in usd per share)	$ 0.67	$ 0.50
Pre-tax net investment income per share - diluted (in usd per share)	0.67	0.50
Net investment income per share – basic (in usd per share)	0.65	0.49
Net investment income per share – diluted (in usd per share)	0.65	0.49
Net increase in net assets from operations – basic (in usd per share)	0.63	0.10
Net increase in net assets from operations – diluted (in usd per share)	$ 0.63	$ 0.10
Weighted average shares outstanding – basic (in share)	37,597,884	25,513,534
Weighted average shares outstanding – diluted (in share)	37,597,884	25,513,534
Non-control/Non-affiliate investments
Interest income:
Interest income	$ 30,640	$ 15,748
Payment-in-kind interest income:
Payment-in-kind interest income	914	416
Dividend income:
Dividend income	499	550
Fee income:
Fee income	945	1,290
Realized (loss) gain
Realized (loss) gain	(5,806)	2,549
Net unrealized appreciation (depreciation) on investments
Unrealized gain (loss)	2,283	(4,551)
Affiliate investments
Interest income:
Interest income	4,179	2,512
Payment-in-kind interest income:
Payment-in-kind interest income	742	271
Dividend income:
Dividend income	60	101
Fee income:
Fee income	157	118
Realized (loss) gain
Realized (loss) gain	(6,655)	15
Net unrealized appreciation (depreciation) on investments
Unrealized gain (loss)	9,169	(714)
Control investments
Dividend income:
Dividend income	2,144	1,535
Fee income:
Fee income	24	0
Net unrealized appreciation (depreciation) on investments
Unrealized gain (loss)	$ 606	$ (5,902)

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Jun. 30, 2023	Jun. 30, 2022
Pay vs Performance Disclosure
Net increase resulting from operations	$ 23,812	$ 2,510

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)			3 Months Ended		12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)	Jul. 18, 2021	Jul. 18, 2011	Jun. 30, 2023 USD ($) investment	Jun. 30, 2022 USD ($) investment	Mar. 31, 2023 USD ($)
Accounting Policies [Abstract]
FDIC Insured amount			$ 7,700,000		$ 8,900,000
FDIC uninsured amount			$ 20,000,000		$ 20,300,000
Concentration Risk [Line Items]
Non-cash interest income percent			2.90%	3.80%
Number of PIK investments \| investment			3	3
Non-cash PIK interest income percent			4.10%	3.00%
Remaining lease term			9 years 3 months 18 days
Interest or penalties expense			$ 0	$ 0
Restricted Stock \| 2010 Plan
Concentration Risk [Line Items]
Right to grant period	10 years	10 years
Right to grant period	10 years	10 years
Percentage of Total Portfolio at Fair Value \| Credit risk \| Investment Owned, Non-accrual Status
Concentration Risk [Line Items]
Percent of total investment portfolio's fair value			1.70%		0.30%
Percentage of Total Portfolio at Cost \| Credit risk \| Investment Owned, Non-accrual Status
Concentration Risk [Line Items]
Percent of total investment portfolio's fair value			2.50%		1.30%

SUBSEQUENT EVENTS (Details) - USD ($)	Aug. 03, 2023	Aug. 02, 2023	Aug. 01, 2023	Nov. 16, 2022	May 11, 2022	May 10, 2022	Aug. 09, 2021	Aug. 08, 2021
Credit Facility \| Line of Credit
Subsequent Event [Line Items]
Maximum borrowing capacity				$ 400,000,000	$ 380,000,000	$ 335,000,000	$ 335,000,000	$ 340,000,000
Accordion feature increase limit				$ 20,000,000
Subsequent Event
Subsequent Event [Line Items]
Dividends (in usd per share)	$ 0.62
Subsequent Event \| Credit Facility \| Line of Credit
Subsequent Event [Line Items]
Maximum borrowing capacity		$ 435,000,000	$ 400,000,000
Accordion feature increase limit		$ 750,000,000
Regular Dividends \| Subsequent Event
Subsequent Event [Line Items]
Dividends (in usd per share)	0.56
Supplemental Dividends \| Subsequent Event
Subsequent Event [Line Items]
Dividends (in usd per share)	$ 0.06

SHAREHOLDERS' EQUITY - Narrative (Details)						3 Months Ended		52 Months Ended
SHAREHOLDERS' EQUITY - Narrative (Details)	Apr. 26, 2023 shares	Nov. 17, 2022 USD ($) $ / shares shares	Jul. 18, 2021	Feb. 04, 2020 USD ($) sales_agent	Jul. 18, 2011	Jun. 30, 2023 USD ($) $ / shares shares	Jun. 30, 2022 USD ($) $ / shares shares	Jun. 30, 2023 USD ($) $ / shares shares	Aug. 02, 2022 USD ($)	Aug. 01, 2022 USD ($)	Aug. 31, 2021 USD ($)	Jul. 28, 2021 USD ($)	May 26, 2021 USD ($)	Mar. 04, 2019 USD ($)
Subsidiary or Equity Method Investee [Line Items]
Repurchase authorized amount											$ 20,000,000	$ 20,000,000
Cancellation of treasury stock (in shares) \| shares	2,339,512
Public Equity Offering
Subsidiary or Equity Method Investee [Line Items]
Number of shares sold (in shares) \| shares		2,534,436
Par value, common stock (in usd per share) \| $ / shares		$ 18.15
Gross proceeds received (in thousands)		$ 46,000,000
Net proceeds received		$ 44,100,000
Equity ATM Program
Subsidiary or Equity Method Investee [Line Items]
Number of shares sold (in shares) \| shares						2,527,458	2,262,852	19,140,580
Gross proceeds received (in thousands)						$ 45,572,000	$ 46,753,000	$ 390,300,000
Net proceeds received						$ 44,888,000	$ 46,052,000	$ 384,000,000
Maximum consideration threshold				$ 100,000,000					$ 650,000,000	$ 250,000,000			$ 250,000,000	$ 50,000,000
Number of additional sales agents \| sales_agent				2
Gross sales commission percentage													1.50%	2.00%
Weighted average price per share (in usd per share) \| $ / shares						$ 18.03	$ 20.66	$ 20.39
Available under the Equity ATM Program						$ 259,700,000		$ 259,700,000
2010 Plan \| Restricted Stock
Subsidiary or Equity Method Investee [Line Items]
Right to grant period			10 years		10 years

COMMITMENTS AND CONTINGENCIES - Unused Commitments (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Mar. 31, 2023
Other Commitments [Line Items]
Total Unfunded Debt Commitments	$ 129,934	$ 124,637
Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	105,187	87,554
Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	24,747	37,083
Total Unfunded Equity Commitments
Other Commitments [Line Items]
Total Unfunded Debt Commitments	537	537
Investment, Identifier [Axis]: AAC New Holdco Inc., Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	166	199
Investment, Identifier [Axis]: ATS Operating, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	1,500	2,000
Investment, Identifier [Axis]: Acacia BuyerCo V LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,500	2,500
Investment, Identifier [Axis]: Acacia BuyerCo V LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,000	2,000
Investment, Identifier [Axis]: Acceleration, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	5,000	5,000
Investment, Identifier [Axis]: Acceleration, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	3,830	1,300
Investment, Identifier [Axis]: Air Conditioning Specialist, Inc., Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	1,450	1,200
Investment, Identifier [Axis]: American Teleconferencing Services, Ltd. (DBA Premiere Global Services, Inc.), Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	0	154
Investment, Identifier [Axis]: ArborWorks, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	894	1,000
Investment, Identifier [Axis]: Bond Brand Loyalty ULC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,000	0
Investment, Identifier [Axis]: Catbird NYC, LLC, Other
Other Commitments [Line Items]
Total Unfunded Debt Commitments	125	125
Investment, Identifier [Axis]: Catbird NYC, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	4,000	4,000
Investment, Identifier [Axis]: Cavalier Buyer, Inc., Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,000	2,000
Investment, Identifier [Axis]: Central Medical Supply LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	1,400	1,400
Investment, Identifier [Axis]: Central Medical Supply LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	1,200	1,200
Investment, Identifier [Axis]: Edge Autonomy Holdings, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	4,000	0
Investment, Identifier [Axis]: Exact Borrower, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	0	2,500
Investment, Identifier [Axis]: Exact Borrower, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,500	2,500
Investment, Identifier [Axis]: FM Sylvan, Inc., Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	10,000	8,000
Investment, Identifier [Axis]: FS Vector LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,000	0
Investment, Identifier [Axis]: GPT Industries, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	3,000	3,000
Investment, Identifier [Axis]: Gains Intermediate, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	5,000	5,000
Investment, Identifier [Axis]: Gains Intermediate, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,500	2,500
Investment, Identifier [Axis]: GrammaTech, Inc., Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,500	2,500
Investment, Identifier [Axis]: Gulf Pacific Acquisition, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	1,212	1,212
Investment, Identifier [Axis]: Gulf Pacific Acquisition, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	707	657
Investment, Identifier [Axis]: HH-Inspire Acquisition, Inc., Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	505	0
Investment, Identifier [Axis]: ISI Enterprises, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,000	2,000
Investment, Identifier [Axis]: ITA Holdings Group, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,969	0
Investment, Identifier [Axis]: ITA Holdings Group, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	3,525	0
Investment, Identifier [Axis]: Infolinks Media Buyco, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	900	2,250
Investment, Identifier [Axis]: Infolinks Media Buyco, LLC, Other
Other Commitments [Line Items]
Total Unfunded Debt Commitments	412	412
Investment, Identifier [Axis]: Island Pump and Tank, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	1,500	1,000
Investment, Identifier [Axis]: KMS, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	0	2,286
Investment, Identifier [Axis]: LKC Technologies, Inc., Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,000	0
Investment, Identifier [Axis]: Lash OpCo, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	445	138
Investment, Identifier [Axis]: Lighting Retrofit International, LLC (DBA Envocore), Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,083	2,083
Investment, Identifier [Axis]: Lightning Intermediate II, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	1,852	1,852
Investment, Identifier [Axis]: Mako Steel LP, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	660	943
Investment, Identifier [Axis]: Microbe Formulas LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	1,627	1,627
Investment, Identifier [Axis]: Muenster Milling Company, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	7,000	7,000
Investment, Identifier [Axis]: NWN Parent Holdings, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	1,200	480
Investment, Identifier [Axis]: New Skinny Mixes, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	3,000	3,000
Investment, Identifier [Axis]: New Skinny Mixes, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,250	4,000
Investment, Identifier [Axis]: NinjaTrader, Inc., Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	0	4,692
Investment, Identifier [Axis]: NinjaTrader, Inc., Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,500	2,500
Investment, Identifier [Axis]: Opco Borrower, LLC (DBA Giving Home Health Care), Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	833	833
Investment, Identifier [Axis]: Outerbox, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,000	2,000
Investment, Identifier [Axis]: Pipeline Technique Ltd., Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,500	2,833
Investment, Identifier [Axis]: RTIC Subsidiary Holdings LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	658	548
Investment, Identifier [Axis]: Roof OpCo, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	3,056	3,056
Investment, Identifier [Axis]: Roseland Management, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	1,700	1,425
Investment, Identifier [Axis]: SIB Holdings, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	187	0
Investment, Identifier [Axis]: Shearwater Research, Inc., Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,446	2,446
Investment, Identifier [Axis]: South Coast Terminals LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	1,935	1,935
Investment, Identifier [Axis]: Spotlight AR, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,000	2,000
Investment, Identifier [Axis]: Systec Corporation (DBA Inspire Automation), Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	200	400
Investment, Identifier [Axis]: Versicare Management LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,600	2,600
Investment, Identifier [Axis]: Versicare Management LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	2,500	2,500
Investment, Identifier [Axis]: Wall Street Prep, Inc., Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	1,000	1,000
Investment, Identifier [Axis]: Well-Foam, Inc., Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	4,500	4,500
Investment, Identifier [Axis]: Winter Services Operations, LLC, Delayed Draw Term Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	0	4,444
Investment, Identifier [Axis]: Winter Services Operations, LLC, Revolving Loans
Other Commitments [Line Items]
Total Unfunded Debt Commitments	$ 4,444	$ 4,444

RELATED PARTY TRANSACTIONS	3 Months Ended
RELATED PARTY TRANSACTIONS	Jun. 30, 2023
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTIONS	RELATED PARTY TRANSACTIONS As a BDC, we are obligated under the 1940 Act to make available to our portfolio companies significant managerial assistance. “Making available significant managerial assistance” refers to any arrangement whereby we offer to provide significant guidance and counsel concerning the management, operations, or business objectives and policies of a portfolio company. We also are deemed to be providing managerial assistance to all portfolio companies that we control, either by ourselves or in conjunction with others. The nature and extent of significant managerial assistance provided by us will vary according to the particular needs of each portfolio company. During each of the three ended June 30, 2023 and 2022, we did not receive any management fees from our portfolio companies. As of June 30, 2023 and March 31, 2023, we had dividends receivable from I-45 SLF LLC of $2.1 million and $1.9 million, respectively, which were included in dividends and interest receivables on the Consolidated Statements of Assets and Liabilities. Additionally, we recognized administrative fee income from I-45 SLF LLC of $24.5 thousand for the three months ended June 30, 2023, which was included in fee income on the Consolidated Statement of Operations.

SUMMARY OF PER SHARE INFORMATION (Details) - $ / shares	3 Months Ended
SUMMARY OF PER SHARE INFORMATION (Details) - $ / shares	Jun. 30, 2023	Jun. 30, 2022	Mar. 31, 2023
Per Share Data:
Investment income (in usd per share)	$ 1.07	$ 0.89
Operating expenses (in usd per share)	(0.40)	(0.39)
Income taxes (in usd per share)	(0.02)	(0.01)
Net investment income (in usd per share)	0.65	0.49
Net realized (loss) gain, net of tax (in usd per share)	(0.34)	0.09
Net unrealized (depreciation) appreciation on investments, net of tax (in usd per share)	0.32	(0.48)
Total increase from investment operations (in usd per share)	0.63	0.10
Accretive effect of share issuances and repurchases (in usd per share)	0.09	0.29
Dividends to shareholders (in usd per share)	(0.59)	(0.63)
Issuance of restricted stock (in usd per share)	(0.13)	(0.13)
Common stock withheld for payroll taxes upon vesting of restricted stock (in usd per share)	(0.05)	(0.01)
Share based compensation expense (in usd per share)	0.02	0.03
Other (in usd per share)	0.04	0.03
(Decrease) increase in net asset value (in usd per share)	0.01	(0.32)
Net asset value
Beginning of period (in usd per share)	16.37	16.86
End of period (in usd per share)	$ 16.38	$ 16.54
Ratios and Supplemental Data
Ratio of operating expenses to average net assets	9.88%	9.12%
Ratio of net investment income to average net assets	15.80%	11.48%
Portfolio turnover	2.26%	6.15%
Total investment return	14.23%	(19.72%)
Total return based on change in NAV	3.67%	1.84%
Per share market value at the end of the period (in usd per share)	$ 19.72	$ 18.42
Weighted average shares outstanding – basic (in share)	37,597,884	25,513,534
Weighted average shares outstanding – diluted (in share)	37,597,884	25,513,534
Common shares outstanding at end of period (in shares)	38,839,918	27,391,000	36,076,425

FAIR VALUE MEASUREMENTS - Summary of Changes in Fair Value of Investments Measured Using Level 3 Inputs (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Gain (Loss), Investment and Derivative, Operating, after Tax	Gain (Loss), Investment and Derivative, Operating, after Tax
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income Extensible List Not Disclosed Flag	YTD Unrealized Appreciation (Depreciation) on Investments held at period end	YTD Unrealized Appreciation (Depreciation) on Investments held at period end
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	$ 1,155,132	$ 879,011
Realized & Unrealized Gains (Losses)	(675)	(2,929)
Purchases of Investments	105,278	135,804
Repayments	(24,876)	(56,008)
PIK Interest Capitalized	1,999	810
Divestitures	(3,402)	(1,749)
Conversion/Exchange of Security2	0	0
Fair value. ending balance	1,233,456	954,939
YTD Unrealized Appreciation (Depreciation) on Investments held at period end	(973)	(1,987)
First lien loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	1,000,984	739,872
Realized & Unrealized Gains (Losses)	558	(1,546)
Purchases of Investments	100,244	132,425
Repayments	(24,785)	(55,937)
PIK Interest Capitalized	1,990	623
Divestitures	0	0
Conversion/Exchange of Security2	(3,791)	0
Fair value. ending balance	1,075,200	815,437
YTD Unrealized Appreciation (Depreciation) on Investments held at period end	446	(613)
Second lien loans
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	35,820	52,645
Realized & Unrealized Gains (Losses)	(876)	(4,145)
Purchases of Investments	62	62
Repayments	(71)	(71)
PIK Interest Capitalized	0	139
Divestitures	0	0
Conversion/Exchange of Security2	0	0
Fair value. ending balance	34,935	48,630
YTD Unrealized Appreciation (Depreciation) on Investments held at period end	(876)	(4,145)
Subordinated debt
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	791	1,317
Realized & Unrealized Gains (Losses)	0	0
Purchases of Investments	0	0
Repayments	(20)	0
PIK Interest Capitalized	9	48
Divestitures	0	0
Conversion/Exchange of Security2	0	0
Fair value. ending balance	780	1,365
YTD Unrealized Appreciation (Depreciation) on Investments held at period end	0	0
Preferred equity
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	63,393	44,663
Realized & Unrealized Gains (Losses)	2,422	(778)
Purchases of Investments	1,844	2,109
Repayments	0	0
PIK Interest Capitalized	0	0
Divestitures	0	0
Conversion/Exchange of Security2	0	0
Fair value. ending balance	67,659	45,994
YTD Unrealized Appreciation (Depreciation) on Investments held at period end	2,422	(778)
Common equity & warrants
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value, beginning balance	54,144	40,514
Realized & Unrealized Gains (Losses)	(2,779)	3,540
Purchases of Investments	3,128	1,208
Repayments	0	0
PIK Interest Capitalized	0	0
Divestitures	(3,402)	(1,749)
Conversion/Exchange of Security2	3,791	0
Fair value. ending balance	54,882	43,513
YTD Unrealized Appreciation (Depreciation) on Investments held at period end	$ (2,965)	$ 3,549

BORROWINGS - Narrative (Details)					1 Months Ended		3 Months Ended
BORROWINGS - Narrative (Details)	May 11, 2022 USD ($)	Aug. 09, 2021 USD ($) lender	Aug. 08, 2021 USD ($) lender	Apr. 20, 2021 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2020 USD ($)	Jun. 30, 2023 USD ($)	Jun. 30, 2022 USD ($)	Mar. 31, 2023 USD ($)	Nov. 22, 2022 USD ($)	Nov. 16, 2022 USD ($) lender	May 10, 2022 USD ($)	Jan. 28, 2022 USD ($)	Nov. 30, 2021 USD ($)	Aug. 31, 2021 USD ($)	May 25, 2021 USD ($)	Feb. 28, 2021 USD ($)	Apr. 25, 2019
Debt Instrument [Line Items]
Asset coverage ratio																		166.00%
Current asset coverage ratio					237.00%		237.00%
Recorded value					$ 672,262,000		$ 672,262,000		$ 637,644,000
Outstanding balance					681,875,000		681,875,000		645,000,000
January 2026 Notes
Debt Instrument [Line Items]
Aggregate principal amount					140,000,000		140,000,000		140,000,000
October 2026 Notes
Debt Instrument [Line Items]
Aggregate principal amount					150,000,000		150,000,000		150,000,000
August 2028 Notes
Debt Instrument [Line Items]
Aggregate principal amount					71,875,000		71,875,000		0
SBA Debentures
Debt Instrument [Line Items]
Aggregate principal amount					125,000,000		125,000,000		120,000,000
Notes \| January 2026 Notes
Debt Instrument [Line Items]
Recorded value					$ 139,135,000		$ 139,135,000		139,051,000
Aggregate principal amount						$ 75,000,000											$ 65,000,000
Fixed interest rate						4.50%
Issuance price percent received																	102.11%
Yield-to-maturity																	4.00%
Weighted average interest rate					4.46%		4.46%
Interest expense							$ 1,700,000	$ 1,700,000
Average borrowings							140,000,000	140,000,000
Redemption price, percentage						100.00%
Outstanding balance					$ 140,000,000		140,000,000		140,000,000
Notes \| January 2026 Notes \| Significant Unobservable Inputs (Level 3)
Debt Instrument [Line Items]
Fair value					118,400,000		118,400,000
Notes \| October 2026 Notes
Debt Instrument [Line Items]
Recorded value					$ 147,448,000		$ 147,448,000		147,263,000
Aggregate principal amount														$ 50,000,000	$ 100,000,000
Fixed interest rate														3.375%	3.375%
Issuance price percent received														99.993%	99.418%
Yield-to-maturity					3.50%		3.50%							3.375%	3.50%
Interest expense							$ 1,500,000	1,400,000
Average borrowings							150,000,000	$ 150,000,000
Redemption price, percentage						100.00%
Outstanding balance					$ 150,000,000		150,000,000		150,000,000
Notes \| October 2026 Notes \| Significant Unobservable Inputs (Level 3)
Debt Instrument [Line Items]
Fair value					127,800,000		127,800,000
Notes \| August 2028 Notes
Debt Instrument [Line Items]
Recorded value					69,327,000		69,327,000
Aggregate principal amount					$ 71,900,000		$ 71,900,000
Fixed interest rate					7.75%		7.75%
Weighted average interest rate					7.75%		7.75%
Interest expense							$ 300,000
Average borrowings					$ 71,900,000
Outstanding balance					71,875,000		71,875,000
Notes \| August 2028 Notes \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Debt Instrument [Line Items]
Fair value					72,300,000		72,300,000
Notes \| August 2028 Notes Overallotment
Debt Instrument [Line Items]
Aggregate principal amount					9,400,000		9,400,000
Unsecured Debt \| SBA Debentures
Debt Instrument [Line Items]
Recorded value					121,352,000		$ 121,352,000		116,330,000
Weighted-average interest rate							3.94%	2.50%
Interest expense							$ 1,400,000	$ 400,000
Average borrowings							123,700,000	51,600,000
Outstanding balance					125,000,000		125,000,000		$ 120,000,000
Unsecured Debt \| SBA Debentures \| SBIC I
Debt Instrument [Line Items]
Debt instrument term				10 years
Regulatory maximum borrowing capacity				$ 175,000,000
Regulatory capital				$ 87,500,000	65,000,000		65,000,000
Leverage commitment amount					130,000,000		130,000,000			$ 50,000,000			$ 40,000,000			$ 40,000,000
Available leverage commitment					65,000,000		65,000,000
Unused commitments					5,000,000		5,000,000
Unsecured Debt \| SBA Debentures \| Significant Unobservable Inputs (Level 3)
Debt Instrument [Line Items]
Fair value					117,800,000		117,800,000
Credit Facility \| Line of Credit
Debt Instrument [Line Items]
LIBOR floor		0.00%	0.00%
Maximum borrowing capacity	$ 380,000,000	$ 335,000,000	$ 340,000,000								$ 400,000,000	$ 335,000,000
Number of lenders \| lender		10	11								11
Covenants increase the minimum obligors		$ 200,000,000	$ 180,000,000
Accordion feature, higher borrowing capacity option	$ 400,000,000
Accordion feature increase limit											$ 20,000,000
Minimum senior coverage ratio	2
Maximum asset coverage ratio	1.50
Interest coverage ratio	2.25
Outstanding advances exceed percentage	90.00%
Minimum liquidity	0.10
Recorded value					195,000,000		195,000,000
Amortization of deferred loan costs							$ 4,900,000	$ 1,900,000
Weighted-average interest rate							7.36%	3.16%
Average outstanding amount							$ 239,700,000	$ 182,900,000
Outstanding balance					$ 195,000,000		$ 195,000,000
Credit Facility \| Line of Credit \| Minimum
Debt Instrument [Line Items]
Commitment fee percentage	0.50%
Credit Facility \| Line of Credit \| Maximum
Debt Instrument [Line Items]
Commitment fee percentage	1.00%
Credit Facility \| Line of Credit \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		2.15%	2.50%

CONSOLIDATED STATEMENTS OF CHANGES IN NET ASSETS - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Investment Company, Net Assets [Roll Forward]
Number of shares, beginning balance (in shares)	36,076,425
Beginning balance	$ 590,408	$ 420,867
Number of shares, beginning balance (in shares)	2,339,512
Issuance of common stock	$ 44,872	46,035
Cancellation of treasury stock	0
Share-based compensation	963	821
Issuance of common stock under restricted stock plan, net of forfeitures	0	0
Common stock withheld for payroll taxes upon vesting of restricted stock	(926)	(641)
Dividends to shareholders	(22,916)	(16,615)
Change in restoration plan liability	(12)	8
Reclassification for certain permanent book-to-tax differences	0	0
Net increase resulting from operations	$ 23,812	$ 2,510
Number of shares, ending balance (in shares)	38,839,918	27,391,000
Ending balance	$ 636,201	$ 452,985
Number of shares, ending balance (in shares)	0
Common Stock
Investment Company, Net Assets [Roll Forward]
Number of shares, beginning balance (in shares)	36,076,425	24,958,520
Beginning balance	$ 9,604	$ 6,825
Issuance of common stock (in shares)	2,527,458	2,262,852
Issuance of common stock	$ 632	$ 566
Cancellation of treasury stock	$ (585)
Issuance of common stock under restricted stock plan, net of forfeitures (in shares)	282,616	199,042
Issuance of common stock under restricted stock plan, net of forfeitures	$ 71	$ 49
Common stock withheld for payroll taxes upon vesting of restricted stock (in shares)	(46,581)	(29,673)
Common stock withheld for payroll taxes upon vesting of restricted stock	$ (12)	$ (7)
Number of shares, ending balance (in shares)	38,839,918	27,390,741
Ending balance	$ 9,710	$ 7,433
Treasury Stock
Investment Company, Net Assets [Roll Forward]
Beginning balance	$ (23,937)	$ (23,937)
Number of shares, beginning balance (in shares)	2,339,512	2,339,512
Cancellation of treasury stock (in shares)	(2,339,512)
Cancellation of treasury stock	$ 23,937
Ending balance	$ 0	$ (23,937)
Number of shares, ending balance (in shares)	0	2,339,512
Additional Paid-In Capital
Investment Company, Net Assets [Roll Forward]
Beginning balance	$ 646,586	$ 448,235
Issuance of common stock	44,240	45,469
Cancellation of treasury stock	(23,352)
Share-based compensation	963	821
Issuance of common stock under restricted stock plan, net of forfeitures	(71)	(49)
Common stock withheld for payroll taxes upon vesting of restricted stock	(914)	(634)
Change in restoration plan liability	(12)	8
Reclassification for certain permanent book-to-tax differences		1
Ending balance	667,440	493,851
Total Distributable Earnings (Loss)
Investment Company, Net Assets [Roll Forward]
Beginning balance	(41,845)	(10,256)
Dividends to shareholders	(22,916)	(16,615)
Reclassification for certain permanent book-to-tax differences		(1)
Net increase resulting from operations	23,812	2,510
Ending balance	$ (40,949)	$ (24,362)

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Jun. 30, 2023
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Cover - shares	3 Months Ended
Cover - shares	Jun. 30, 2023	Aug. 04, 2023
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2023
Document Transition Report	false
Entity File Number	814-00061
Entity Registrant Name	CAPITAL SOUTHWEST CORPORATION
Entity Incorporation, State or Country Code	TX
Entity Tax Identification Number	75-1072796
Entity Address, Address Line One	8333 Douglas Avenue
Entity Address, Address Line Two	Suite 1100
Entity Address, City or Town	Dallas
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75225
City Area Code	214
Local Phone Number	238-5700
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		39,939,918
Entity Central Index Key	0000017313
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--03-31
Common Stock
Document Information [Line Items]
Title of 12(b) Security	Common Stock, $0.25 par value per share
Trading Symbol	CSWC
Security Exchange Name	NASDAQ
August 2028 Notes
Document Information [Line Items]
Title of 12(b) Security	7.75% Notes due 2028
Trading Symbol	CSWCZ
Security Exchange Name	NASDAQ

INCOME TAXES - Net Assets Resulting From Operations To Estimated RIC Taxable Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Income Tax Disclosure [Abstract]
Net increase resulting from operations	$ 23,812	$ 2,510
Net unrealized depreciation (appreciation) on investments	(12,038)	12,248
(Expense/loss) income/gain recognized for tax on pass-through entities	(4,202)	40
(Gain) loss recognized on dispositions	(1,641)	0
Capital loss carryover	17,932	(1,567)
Net operating income - wholly-owned subsidiary	(1,796)	(1,534)
Dividend income from wholly-owned subsidiary	0	907
Non-deductible tax expense	93	73
Loss on extinguishment of debt	(682)	(682)
Non-deductible compensation	892	822
Compensation related book/tax differences	(5,824)	(5,529)
Interest on non-accrual loans	1,415	1,128
Other book/tax differences	1,610	257
Estimated distributable income before deductions for distributions	19,571	$ 8,673
Capital loss carryover	$ 49,100