Cover - shares	9 Months Ended
	Dec. 31, 2022	Jan. 27, 2023
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Dec. 31, 2022
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
Title of 12(b) Security	Common Stock, $0.25 par value per share
Trading Symbol	CSWC
Security Exchange Name	NASDAQ
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		34,559,034
Entity Central Index Key	0000017313
Amendment Flag	false
Current Fiscal Year End Date	--03-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q3