Changes in Level 3 Assets and Liabilities (Details 3) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets measured at fair value using significant unobservable inputs, value at beginning of period	$ 53,736	$ 79,546	$ 63,118	$ 84,839
Purchases	650	78	1,893	1,046
Sales	(380)	(1,023)	(6,557)	(6,881)
Redemptions/Settlements/Other	(1,655)	(3,806)	(6,615)	(4,370)
Transfers, Net	0	0	0	0
Realized and unrealized gains/(losses), net	(1,201)	(1,001)	(689)	(840)
Assets measured at fair value using significant unobservable inputs, value at end of period	51,150	73,794	51,150	73,794
Consolidated Entity Excluding Variable Interest Entities (VIE) [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Unrealized Gains (Losses) Relating to Fair Value Measurements Using Unobservable Inputs Assets and Liabilities Still Held at Reporting Date	1,218	131	(2,822)	(1,200)
Proprietary Fund Product And Other Investments [Member] | Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets measured at fair value using significant unobservable inputs, value at beginning of period	191	179	186	190
Purchases	0	0	0	0
Sales	(35)	(9)	(42)	(19)
Redemptions/Settlements/Other	0	0	0	0
Transfers, Net	0	0	0	0
Realized and unrealized gains/(losses), net	8	0	20	(1)
Assets measured at fair value using significant unobservable inputs, value at end of period	164	170	164	170
Investment In Partnerships And Limited Liability Companies [Member] | Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets measured at fair value using significant unobservable inputs, value at beginning of period	11,907	21,654	14,511	21,586
Purchases	0	0	0	0
Sales	0	(24)	0	(24)
Redemptions/Settlements/Other	(2)	(3,443)	(2,530)	(3,443)
Transfers, Net	0	0	0	0
Realized and unrealized gains/(losses), net	(615)	(505)	(691)	(437)
Assets measured at fair value using significant unobservable inputs, value at end of period	11,290	17,682	11,290	17,682
Equity Method Investments In Partnerships And LLCs [Member] | Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets measured at fair value using significant unobservable inputs, value at beginning of period	41,562	57,621	48,344	62,973
Purchases	650	78	1,893	1,046
Sales	(345)	(990)	(6,515)	(6,838)
Redemptions/Settlements/Other	(1,653)	(363)	(4,085)	(927)
Transfers, Net	0	0	0	0
Realized and unrealized gains/(losses), net	(595)	(489)	(18)	(397)
Assets measured at fair value using significant unobservable inputs, value at end of period	39,619	55,857	39,619	55,857
Other Investments [Member] | Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Assets measured at fair value using significant unobservable inputs, value at beginning of period	76	92	77	90
Purchases	0	0	0	0
Sales	0	0	0	0
Redemptions/Settlements/Other	0	0	0	0
Transfers, Net	0	0	0	0
Realized and unrealized gains/(losses), net	1	(7)	0	(5)
Assets measured at fair value using significant unobservable inputs, value at end of period	77	85	77	85
Contingent Consideration Liability | Consolidated Entity Excluding Consolidated Investment Vehicles Before Eliminations [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Liabilities measured at fair value using significant unobservable inputs, value at beginning of period	(92,744)	(43,984)	(110,784)	(29,553)
Purchases	0	0	0	(13,370)
Redemptions/Settlements/Other	0	0	22,765	0
Realized and unrealized gains/(losses), net	2,525	1,331	(2,200)	270
Liabilities measured at fair value using significant unobservable inputs, value at end of period	$ (90,219)	$ (42,653)	$ (90,219)	$ (42,653)