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N-2 - $ / shares | 6 Months Ended |  |  |
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Sep. 30, 2023 | Mar. 31, 2023 | Sep. 30, 2022 | Mar. 31, 2022
Cover [Abstract] |  |  |  |
Entity Central Index Key | 0000017313 |  |  |
Amendment Flag | false |  |  |
Securities Act File Number | 814-00061 |  |  |
Document Type | 10-Q |  |  |
Entity Registrant Name | CAPITAL SOUTHWEST CORPORATION |  |  |
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 Emerging Growth Company | false |  |  |
General Description of Registrant [Abstract] |  |  |  |
Investment Objectives and Practices [Text Block] | We are an internally managed closed-end, non-diversified management investment company that has elected to be regulated as a BDC under the 1940 Act. We specialize in providing customized debt and equity financing to LMM companies and debt capital to UMM companies in a broad range of investment segments located primarily in the United States. Our investment objective is to produce attractive risk-adjusted returns by generating current income from our debt investments and capital appreciation from our equity and equity related investments. Our investment strategy is to partner with business owners, management teams and financial sponsors to provide flexible financing solutions to fund growth, changes of control, or other corporate events. We invest primarily in senior debt securities, secured by security interests in portfolio company assets. We also invest in equity interests in our portfolio companies alongside our debt securities. 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. We primarily target senior debt and equity investments in LMM companies, and opportunistically target first and second lien loans in UMM companies. Our target LMM companies typically have annual EBITDA 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 our UMM investments typically range in size from $5.0 million to $20.0 million. We seek to fill the financing gap for LMM companies, which, historically, have had more limited access to financing from commercial banks and other traditional sources. The underserved nature of the LMM creates the opportunity for us to meet the financing needs of LMM companies while also negotiating favorable transaction terms and equity participations. Our ability to invest across a LMM company’s capital structure, from secured loans to equity securities, allows us to offer portfolio companies a comprehensive suite of financing options. Providing customized financing solutions is important to LMM companies. We generally seek to partner directly with financial sponsors, entrepreneurs, management teams and business owners in making our investments. Our LMM debt investments typically include senior loans with a first lien on the assets of the portfolio company. Our LMM debt investments typically have a term of between five and seven years from the original investment date. We also often seek to invest in the equity securities of our LMM portfolio companies. Our investments in UMM companies primarily consist of direct investments in or secondary purchases of interest bearing debt securities in privately held companies that are generally larger in size than the LMM companies included in our portfolio. Our UMM debt investments are generally secured by either a first or second priority lien on the assets of the portfolio company and typically have an expected duration of between three and seven years from the original investment date. Because we are internally managed, we do not pay any external investment advisory fees, but instead directly incur the operating costs associated with employing investment and portfolio management professionals. We believe that our internally managed structure provides us with a beneficial operating expense structure when compared to other publicly traded and privately held investment firms that are externally managed, and our internally managed structure allows us the opportunity to leverage our non-interest operating expenses as we grow our investment portfolio. For the six months ended September 30, 2023 and 2022, the ratio of our last twelve months ("LTM") operating expenses, excluding interest expense, as a percentage of our LTM average total assets was 1.84% and 1.99%, respectively. |  |  |
Risk Factors [Table Text Block] | Risk Factors Investing in our common stock involves a number of significant risks. There have been no material changes to the risk factors as previously disclosed in our Annual Report on Form 10-K for the fiscal year ended March 31, 2023 that we filed with the SEC on May 23, 2023, other than the risk factor listed below: The alternative reference rates that have replaced LIBOR in our credit arrangements and other financial instruments may not yield the same or similar economic results as LIBOR over the life of such transactions. The London Interbank Offered Rate (“LIBOR”) is an index rate that historically was widely used in lending transactions and was a common reference rate for setting the floating interest rate on private loans. LIBOR was typically the reference rate used in floating-rate loans extended to our portfolio companies. The ICE Benchmark Administration (“IBA”) (the entity that is responsible for calculating LIBOR) ceased providing overnight, one, three, six and twelve months USD LIBOR tenors on June 30, 2023. In addition, the United Kingdom’s Financial Conduct Authority (“FCA”), which oversees the IBA, now prohibits entities supervised by the FCA from using LIBORs, including USD LIBOR, except in very limited circumstances. In the United States, the Secured Overnight Financing Rate (“SOFR”) is the preferred alternative rate for LIBOR. SOFR is a measure of the cost of borrowing cash overnight, collateralized by U.S. Treasury securities, and is based on directly observable U.S. Treasury-backed repurchase transactions. SOFR is published by the Federal Reserve Bank of New York each U.S. Government Securities Business Day, for transactions made on the immediately preceding U.S. Government Securities Business Day. Alternative reference rates that may replace LIBOR, including SOFR for USD transactions, may not yield the same or similar economic results as LIBOR over the lives of such transactions. Substantially all of our loans that referenced LIBOR have been amended to reference the forward-looking term rate published by CME Group Benchmark Administration Limited based on the secured overnight financing rate (“CME Term SOFR”). CME Term SOFR rates are forward-looking rates that are derived by compounding projected overnight SOFR rates over one, three, and six months taking into account the values of multiple consecutive, executed, one-month and three-month CME Group traded SOFR futures contracts and, in some cases, over-the-counter SOFR Overnight Indexed Swaps as an indicator of CME Term SOFR reference rate values. CME Term SOFR and the inputs on which it is based are derived from SOFR. Since CME Term SOFR is a relatively new market rate, there will likely be no established trading market for credit agreements or other financial instruments when they are issued, and an established market may never develop or may not be liquid. Market terms for instruments referencing CME Term SOFR rates may be lower than those of later-issued CME Term SOFR indexed instruments. Similarly, if CME Term SOFR does not prove to be widely used, the trading price of instruments referencing CME Term SOFR may be lower than those of instruments indexed to indices that are more widely used. |  |  |
NAV Per Share | $ 16.46 | $ 16.37 | $ 16.53 | $ 16.86
Capital Stock, Long-Term Debt, and Other Securities [Abstract] |  |  |  |
Long Term Debt [Table Text Block] | 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 September 30, 2023, the Company’s asset coverage was 229%. 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 2, 2023, the Company entered into the Third Amended and Restated Senior Secured Revolving Credit Agreement (as amended or otherwise modified from time to time, the "Credit Agreement"). Borrowings under the Credit Facility accrue interest at a rate equal to the applicable Adjusted Term SOFR plus 2.15% per annum. The Credit Agreement (1) increased commitments under the Credit Facility from $400 million to $435 million from a diversified group of lenders; (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. 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 2.00 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%, and (7) maintaining an interest coverage ratio of at least 2.00 to 1. 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 September 30, 2023, substantially all of the Company’s assets were pledged as collateral for the Credit Facility, except for assets held by SBIC I. At September 30, 2023, CSWC had $250.0 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 $4.3 million and $9.3 million for the three and six months ended September 30, 2023, respectively. For the three and six months ended September 30, 2022, CSWC recognized interest expense of $2.9 million and $4.8 million, respectively. The weighted average interest rate on the Credit Facility was 7.70% and 7.52% and for the three and six months ended September 30, 2023, respectively. For the three and six months ended September 30, 2022, the weighted average interest rate on the Credit Facility was 4.46% and 3.86%, respectively. Average borrowings for the three and six months ended September 30, 2023 were $185.1 million and $106.1 million, respectively. For the three and six months ended September 30, 2022, average borrowings were $214.6 million and $198.8 million, respectively. As of September 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 September 30, 2023, the carrying amount of the January 2026 Notes was $139.2 million on an aggregate principal amount of $140.0 million at a weighted average effective yield of 4.46%. As of September 30, 2023, the fair value of the January 2026 Notes was $117.3 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 and $3.3 million, respectively, for each of the three and six months ended September 30, 2023 and 2022. For each of the three and six months ended September 30, 2023 and 2022, average borrowings were $140.0 million. The indenture governing the January 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 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 In August 2021, the Company issued $100.0 million in aggregate principal amount of 3.375% Notes due 2026 (the "Existing October 2026 Notes"). The Existing October 2026 Notes were issued at a price of 99.418% of the aggregate principal amount of the Existing October 2026 Notes, resulting in a yield-to-maturity of 3.5%. In November 2021, the Company issued an additional $50.0 million in aggregate principal amount of the October 2026 Notes (the "Additional October 2026 Notes" together with the Existing October 2026 Notes, the "October 2026 Notes"). The Additional October 2026 Notes were issued at a price of 99.993% of the aggregate principal amount, resulting in a yield-to-maturity of approximately 3.375% at issuance. The Additional October 2026 Notes are treated as a single series with the Existing October 2026 Notes under the indenture and have the same terms as the Existing October 2026 Notes. The October 2026 Notes mature on October 1, 2026 and may be redeemed in whole or in part at any time prior to July 1, 2026, at par plus a "make-whole" premium, and thereafter at par. The October 2026 Notes bear interest at a rate of 3.375% per year, payable semi-annually in arrears on April 1 and October 1 of each year. The October 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 September 30, 2023, the carrying amount of the October 2026 Notes was $147.6 million on an aggregate principal amount of $150.0 million at a weighted average effective yield of 3.5%. As of September 30, 2023, the fair value of the October 2026 Notes was $126.1 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 $2.9 million for the three and six months ended September 30, 2023, respectively. For the three and six months ended September 30, 2022, the Company recognized interest expense of $1.4 million and $2.9 million, respectively. For each of the three and six months ended September 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 September 30, 2023, the carrying amount of the August 2028 Notes was $69.4 million on an aggregate principal amount of $71.9 million at a weighted average effective yield of 7.75%. As of September 30, 2023, the fair value of the August 2028 Notes was $73.6 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 $1.5 million and $1.8 million for the three and six months ended September 30, 2023, respectively. Since the issuance of the August 2028 Notes on June 14, 2023 through September 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. 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 September 30, 2023, SBIC I had regulatory capital of $87.5 million and leverageable capital of $79.0 million. As of September 30, 2023, all approved SBA Debenture commitments have been utilized. As of September 30, 2023, the carrying amount of SBA Debentures was $126.4 million on an aggregate principal amount of $130.0 million. As of September 30, 2023, the fair value of the SBA Debentures was $116.2 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 $1.5 million and $2.9 million for the three and six months ended September 30, 2023, respectively. For the three and six months ended September 30, 2022, the Company recognized interest expense of $0.6 million and $1.0 million, respectively. The weighted average interest rate on the SBA Debentures was 4.23% and 4.09% for the three and six months ended September 30, 2023, respectively. For the three and six months ended September 30, 2022, the weighted average interest rate on the SBA Debentures was 2.58% and 2.55%, respectively. For the three and six months ended September 30, 2023, average borrowings were $128.2 million and $126.0 million, respectively. For the three and six months ended September 30, 2022, average borrowings were $80.0 million and $65.9 million, respectively. As of September 30, 2023, the Company's issued and outstanding SBA Debentures mature as follows (amounts in thousands):
Pooling Date (1) |  | Maturity Date |  | Fixed Interest Rate |  | September 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 |
9/20/2023 |  | 9/1/2033 |  | 5.735% |  | 10,000 |
|  |  |  |  |  | $ | 130,000 |
(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. |  |  |
Alternative Reference Rates Economic Results Risk [Member] |  |  |  |
General Description of Registrant [Abstract] |  |  |  |
Risk [Text Block] | The alternative reference rates that have replaced LIBOR in our credit arrangements and other financial instruments may not yield the same or similar economic results as LIBOR over the life of such transactions. The London Interbank Offered Rate (“LIBOR”) is an index rate that historically was widely used in lending transactions and was a common reference rate for setting the floating interest rate on private loans. LIBOR was typically the reference rate used in floating-rate loans extended to our portfolio companies. The ICE Benchmark Administration (“IBA”) (the entity that is responsible for calculating LIBOR) ceased providing overnight, one, three, six and twelve months USD LIBOR tenors on June 30, 2023. In addition, the United Kingdom’s Financial Conduct Authority (“FCA”), which oversees the IBA, now prohibits entities supervised by the FCA from using LIBORs, including USD LIBOR, except in very limited circumstances. In the United States, the Secured Overnight Financing Rate (“SOFR”) is the preferred alternative rate for LIBOR. SOFR is a measure of the cost of borrowing cash overnight, collateralized by U.S. Treasury securities, and is based on directly observable U.S. Treasury-backed repurchase transactions. SOFR is published by the Federal Reserve Bank of New York each U.S. Government Securities Business Day, for transactions made on the immediately preceding U.S. Government Securities Business Day. Alternative reference rates that may replace LIBOR, including SOFR for USD transactions, may not yield the same or similar economic results as LIBOR over the lives of such transactions. Substantially all of our loans that referenced LIBOR have been amended to reference the forward-looking term rate published by CME Group Benchmark Administration Limited based on the secured overnight financing rate (“CME Term SOFR”). CME Term SOFR rates are forward-looking rates that are derived by compounding projected overnight SOFR rates over one, three, and six months taking into account the values of multiple consecutive, executed, one-month and three-month CME Group traded SOFR futures contracts and, in some cases, over-the-counter SOFR Overnight Indexed Swaps as an indicator of CME Term SOFR reference rate values. CME Term SOFR and the inputs on which it is based are derived from SOFR. Since CME Term SOFR is a relatively new market rate, there will likely be no established trading market for credit agreements or other financial instruments when they are issued, and an established market may never develop or may not be liquid. Market terms for instruments referencing CME Term SOFR rates may be lower than those of later-issued CME Term SOFR indexed instruments. Similarly, if CME Term SOFR does not prove to be widely used, the trading price of instruments referencing CME Term SOFR may be lower than those of instruments indexed to indices that are more widely used. |  |  |
January 2026 Notes [Member] |  |  |  |
Capital Stock, Long-Term Debt, and Other Securities [Abstract] |  |  |  |
Long Term Debt, Title [Text Block] | January 2026 Notes |  |  |
Long Term Debt, Structuring [Text Block] | 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 September 30, 2023, the carrying amount of the January 2026 Notes was $139.2 million on an aggregate principal amount of $140.0 million at a weighted average effective yield of 4.46%. As of September 30, 2023, the fair value of the January 2026 Notes was $117.3 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 and $3.3 million, respectively, for each of the three and six months ended September 30, 2023 and 2022. For each of the three and six months ended September 30, 2023 and 2022, average borrowings were $140.0 million. |  |  |
Long Term Debt, Dividends and Covenants [Text Block] | The indenture governing the January 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 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 [Member] |  |  |  |
Capital Stock, Long-Term Debt, and Other Securities [Abstract] |  |  |  |
Long Term Debt, Title [Text Block] | October 2026 Notes |  |  |
Long Term Debt, Structuring [Text Block] | In August 2021, the Company issued $100.0 million in aggregate principal amount of 3.375% Notes due 2026 (the "Existing October 2026 Notes"). The Existing October 2026 Notes were issued at a price of 99.418% of the aggregate principal amount of the Existing October 2026 Notes, resulting in a yield-to-maturity of 3.5%. In November 2021, the Company issued an additional $50.0 million in aggregate principal amount of the October 2026 Notes (the "Additional October 2026 Notes" together with the Existing October 2026 Notes, the "October 2026 Notes"). The Additional October 2026 Notes were issued at a price of 99.993% of the aggregate principal amount, resulting in a yield-to-maturity of approximately 3.375% at issuance. The Additional October 2026 Notes are treated as a single series with the Existing October 2026 Notes under the indenture and have the same terms as the Existing October 2026 Notes. The October 2026 Notes mature on October 1, 2026 and may be redeemed in whole or in part at any time prior to July 1, 2026, at par plus a "make-whole" premium, and thereafter at par. The October 2026 Notes bear interest at a rate of 3.375% per year, payable semi-annually in arrears on April 1 and October 1 of each year. The October 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 September 30, 2023, the carrying amount of the October 2026 Notes was $147.6 million on an aggregate principal amount of $150.0 million at a weighted average effective yield of 3.5%. As of September 30, 2023, the fair value of the October 2026 Notes was $126.1 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 $2.9 million for the three and six months ended September 30, 2023, respectively. For the three and six months ended September 30, 2022, the Company recognized interest expense of $1.4 million and $2.9 million, respectively. For each of the three and six months ended September 30, 2023 and 2022, average borrowings were $150.0 million. |  |  |
Long Term Debt, Dividends and Covenants [Text Block] | 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 [Member] |  |  |  |
Capital Stock, Long-Term Debt, and Other Securities [Abstract] |  |  |  |
Long Term Debt, Title [Text Block] | August 2028 Notes |  |  |
Long Term Debt, Structuring [Text Block] | 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 September 30, 2023, the carrying amount of the August 2028 Notes was $69.4 million on an aggregate principal amount of $71.9 million at a weighted average effective yield of 7.75%. As of September 30, 2023, the fair value of the August 2028 Notes was $73.6 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 $1.5 million and $1.8 million for the three and six months ended September 30, 2023, respectively. Since the issuance of the August 2028 Notes on June 14, 2023 through September 30, 2023, average borrowings were $71.9 million. |  |  |
Long Term Debt, Dividends and Covenants [Text Block] | 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. |  |  |
Credit Facility [Member] |  |  |  |
Capital Stock, Long-Term Debt, and Other Securities [Abstract] |  |  |  |
Long Term Debt, Title [Text Block] | Credit Facility |  |  |
Long Term Debt, Structuring [Text Block] | 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. 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 September 30, 2023, substantially all of the Company’s assets were pledged as collateral for the Credit Facility, except for assets held by SBIC I. At September 30, 2023, CSWC had $250.0 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 $4.3 million and $9.3 million for the three and six months ended September 30, 2023, respectively. For the three and six months ended September 30, 2022, CSWC recognized interest expense of $2.9 million and $4.8 million, respectively. The weighted average interest rate on the Credit Facility was 7.70% and 7.52% and for the three and six months ended September 30, 2023, respectively. For the three and six months ended September 30, 2022, the weighted average interest rate on the Credit Facility was 4.46% and 3.86%, respectively. Average borrowings for the three and six months ended September 30, 2023 were $185.1 million and $106.1 million, respectively. For the three and six months ended September 30, 2022, average borrowings were $214.6 million and $198.8 million, respectively. As of September 30, 2023 and 2022, CSWC was in compliance with all financial covenants under the Credit Agreement. |  |  |
Long Term Debt, Dividends and Covenants [Text Block] | 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. |  |  |
SBA Debentures [Member] |  |  |  |
Capital Stock, Long-Term Debt, and Other Securities [Abstract] |  |  |  |
Long Term Debt, Title [Text Block] | SBA Debentures |  |  |
Long Term Debt, Structuring [Text Block] | 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. 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 September 30, 2023, SBIC I had regulatory capital of $87.5 million and leverageable capital of $79.0 million. As of September 30, 2023, all approved SBA Debenture commitments have been utilized. As of September 30, 2023, the carrying amount of SBA Debentures was $126.4 million on an aggregate principal amount of $130.0 million. As of September 30, 2023, the fair value of the SBA Debentures was $116.2 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 $1.5 million and $2.9 million for the three and six months ended September 30, 2023, respectively. For the three and six months ended September 30, 2022, the Company recognized interest expense of $0.6 million and $1.0 million, respectively. The weighted average interest rate on the SBA Debentures was 4.23% and 4.09% for the three and six months ended September 30, 2023, respectively. For the three and six months ended September 30, 2022, the weighted average interest rate on the SBA Debentures was 2.58% and 2.55%, respectively. For the three and six months ended September 30, 2023, average borrowings were $128.2 million and $126.0 million, respectively. For the three and six months ended September 30, 2022, average borrowings were $80.0 million and $65.9 million, respectively. As of September 30, 2023, the Company's issued and outstanding SBA Debentures mature as follows (amounts in thousands):
Pooling Date (1) |  | Maturity Date |  | Fixed Interest Rate |  | September 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 |
9/20/2023 |  | 9/1/2033 |  | 5.735% |  | 10,000 |
|  |  |  |  |  | $ | 130,000 |
(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. |  |  |

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