Fair Value of Assets and Liabilities of CIVs by Level (Details 3) - Consolidated Investment Vehicles [Member] - USD ($) $ in Thousands		Sep. 30, 2017	Mar. 31, 2017
Proprietary Funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure		$ 40,775	$ 28,300
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure		90,793	33,991
Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	[1]		$ 24,734
Estimate of Fair Value Measurement [Member] | Hedge Funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	[1]	$ 22,465

[1] Redemption restrictions: 4% daily redemption; 7% monthly redemption; 48% quarterly redemption; and 41% are subject to three to five-year lock-up or side pocket provisions.