UNDISTRIBUTED NET REALIZED GAINS (LOSSES) ON INVESTMENTS (Details) (USD $)	Sep. 30, 2012	Mar. 31, 2012
UNDISTRIBUTED NET REALIZED GAINS (LOSSES) ON INVESTMENTS [Abstract]
Undistributed long term capital gains	$ 553,689	$ 498,438

The accumulated net realized gain (loss) from investments during the period.

No definition available.

Name:	cswc_AccumulatedLongTermCapitalGain
Namespace Prefix:	cswc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant