SUMMARY OF PER SHARE INFORMATION (Details) (USD $)	3 Months Ended				6 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
SUMMARY OF PER SHARE INFORMATION [Abstract]
Investment income (in dollars per share)	$ 0.35		$ 0.34		$ 0.74		$ 0.65
Operating expenses (in dollars per share)	$ (0.37)		$ (0.32)		$ (0.75)		$ (0.63)
Income taxes (in dollars per share)	$ (0.01)		$ (0.01)		$ (0.01)		$ (0.01)
Net investment income (in dollars per share)	$ (0.03)		$ 0.01		$ (0.02)		$ 0.01
Distributions from undistributed net investment income (in dollars per share)	$ 0		$ 0		$ (18)		$ (0.4)
Net realized gain net of tax (in dollars per share)	$ 0		$ 4.88		$ 17.62		$ 3.31
Net increase (decrease) in unrealized appreciation of investments (in dollars per share)	$ 13.26		$ (11.74)		$ (7.43)		$ (12.95)
Exercise of employee stock options (in dollars per share)	$ 0		$ (0.03)		$ (0.74)		$ (0.03)
Stock option expense (in dollars per share)	$ 0		$ 0.07		$ 0.08		$ 0.13
Other (in dollars per share)	$ (0.31)	[1]	$ 0	[1]	$ (0.31)	[1]	$ 0	[1]
Increase (decrease) in net asset value (in dollars per share)	$ 12.92		$ (6.81)		$ (8.8)		$ (9.93)
Net asset value, Beginning of period (in dollars per share)	$ 145.73		$ 140.56		$ 167.45		$ 143.68
Net asset value, End of period (in dollars per share)	$ 158.65		$ 133.75		$ 158.65		$ 133.75

[1] Reflects impact of the different share amounts as a result of issuance or forfeiture of restricted stock during the period.