Variable Interest Entities and Consolidation of Investment Vehicles (Details 5) (CIVs, Significant unobservable inputs (Level 3), USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Hedge funds
ASSETS:
Assets measured at fair value using significant unobservable inputs, value at beginning of period	$ 24,116	$ 34,272
Purchases	1,980	17,018
Sales	(6,602)	(32,058)
Settlements and Other	0
Transfers Into Level 3		3,302
Transfers Out of Level 3		(3,316)
Transfers, Net	0
Realized and unrealized gains/(losses), net	(46)	4,898
Assets measured at fair value using significant unobservable inputs, value at end of period	19,448	24,116
Private equity funds
ASSETS:
Assets measured at fair value using significant unobservable inputs, value at beginning of period	25,071	17,879
Purchases	2,622	4,889
Sales	(2,030)	(762)
Settlements and Other	0
Transfers Into Level 3		0
Transfers Out of Level 3		0
Transfers, Net	0
Realized and unrealized gains/(losses), net	1,319	3,065
Assets measured at fair value using significant unobservable inputs, value at end of period	26,982	25,071
Total assets
ASSETS:
Assets measured at fair value using significant unobservable inputs, value at beginning of period	49,187	52,151
Purchases	4,602	21,907
Sales	(8,632)	(32,820)
Settlements and Other	0
Transfers Into Level 3		3,302
Transfers Out of Level 3		(3,316)
Transfers, Net	0
Realized and unrealized gains/(losses), net	1,273	7,963
Assets measured at fair value using significant unobservable inputs, value at end of period	46,430	49,187
CLO debt
LIABILITIES:
Liabilities measured at fair value using significant unobservable inputs, value at beginning of period	(271,707)	(278,320)
Purchases	0	0
Sales	0	0
Settlements/Other	75,798
Transfers Into Level 3		0
Transfers Out of Level 3		0
Transfers, Net	0
Realized and unrealized gains/(losses), net	(11,926)	6,613
Liabilities measured at fair value using significant unobservable inputs, value at end of period	(207,835)	(271,707)
Gain (Loss) on Investments
Fair Value Disclosures [Abstract]
Total realized and unrealized gains (losses), net	(10,653)	14,576
Unrealized gains (losses) on Level 3 assets and liabilities still held at the reporting date	$ (11,842)	$ 7,297