XML 20 R1.htm IDEA: XBRL DOCUMENT

Cover - USD ($)	12 Months Ended
Cover - USD ($)	Mar. 31, 2025	May 16, 2025	Sep. 30, 2024
Document Information [Line Items]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Mar. 31, 2025
Current Fiscal Year End Date	--03-31
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 Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 1,152,736,688
Entity Common Stock, Shares Outstanding		53,710,750
Documents Incorporated by Reference	Documents Incorporated by Reference Portions of the registrant’s definitive Proxy Statement for its 2025 Annual Meeting of Shareholders to be filed not later than 120 days after the end of the fiscal year covered by this Annual Report on Form 10-K are incorporated by reference into Part III of this Annual Report on Form 10-K.
Entity Central Index Key	0000017313
Amendment Flag	false
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	FY
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