Cover - shares	6 Months Ended
	Sep. 30, 2023	Oct. 27, 2023
Document Information [Line Items]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 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		39,951,118
Entity Central Index Key	0000017313
Amendment Flag	false
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q2
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