Variable Interest Entities and Consolidation of Investment Vehicles (Details 5) (CIVs, Significant unobservable inputs (Level 3), USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011
ASSETS:
Assets measured at fair value using significant unobservable inputs, value at beginning of period	$ 44,988	$ 56,840	$ 49,187	$ 52,151
Purchases	3,207	3,794	3,703	18,467
Sales	(1,686)	(10,954)	(5,633)	(26,461)
Settlements and Other	0		0
Transfers Into Level 3				1,057
Transfers Out of Level 3				(1,057)
Transfers, Net	0	0	0
Realized and unrealized gains/(losses), net	594	738	(154)	6,261
Assets measured at fair value using significant unobservable inputs, value at end of period	47,103	50,418	47,103	50,418
Hedge funds
ASSETS:
Assets measured at fair value using significant unobservable inputs, value at beginning of period	21,751	33,327	24,116	34,272
Purchases	426	3,794	922	14,493
Sales	(1,359)	(10,954)	(3,276)	(26,461)
Settlements and Other	0		0
Transfers Into Level 3				1,057
Transfers Out of Level 3				(1,057)
Transfers, Net	0	0	0
Realized and unrealized gains/(losses), net	(22)	380	(966)	4,243
Assets measured at fair value using significant unobservable inputs, value at end of period	20,796	26,547	20,796	26,547
Private equity funds
ASSETS:
Assets measured at fair value using significant unobservable inputs, value at beginning of period	23,237	23,513	25,071	17,879
Purchases	2,781	0	2,781	3,974
Sales	(327)	0	(2,357)	0
Settlements and Other	0		0
Transfers Into Level 3				0
Transfers Out of Level 3				0
Transfers, Net	0	0	0
Realized and unrealized gains/(losses), net	616	358	812	2,018
Assets measured at fair value using significant unobservable inputs, value at end of period	26,307	23,871	26,307	23,871
CLO debt
LIABILITIES:
Liabilities measured at fair value using significant unobservable inputs, value at beginning of period	(277,309)	(267,714)	(271,707)	(278,320)
Purchases	0	0	0	0
Sales	0	0	0	0
Settlements/Other	32,821		32,821
Transfers Into Level 3				0
Transfers Out of Level 3				0
Transfers, Net	0	0	0
Realized and unrealized gains/(losses), net	(5,672)	2,236	(11,274)	12,842
Liabilities measured at fair value using significant unobservable inputs, value at end of period	(250,160)	(265,478)	(250,160)	(265,478)
Gain (Loss) on Investments
Fair Value Disclosures [Abstract]
Total realized and unrealized gains (losses), net	(5,078)	2,974	(11,428)	19,103
Unrealized gains (losses) on Level 3 assets and liabilities still held at the reporting date	$ (4,783)	$ 2,192	$ (11,746)	$ 13,127