Variable Interest Entities and Consolidation of Investment Vehicles Information about Investments in CIV's (Details) $ in Thousands	3 Months Ended
	Sep. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Sep. 30, 2016	Jul. 26, 2017 USD ($)	Jun. 06, 2017 USD ($)
Variable Interest Entity
Employee Owned Funds	1	1	1
Variable Interest Entity, Primary Beneficiary, Number of Collateralized Securites Vehicles	3	3	9
Number of Sponsored Investment Fund Vie	2	3	3
Number of sponsored ETF's considered VIE's	2	0	0
Derivative, Notional Amount				$ 23,096	$ 20,253
Consolidated Investment Vehicles [Member] | Proprietary Funds [Member]
Variable Interest Entity
Assets, Fair Value Disclosure	$ 40,775	$ 28,300
Future [Member]
Variable Interest Entity
Derivative, Notional Amount	147,988
Derivative Financial Instruments, Assets [Member] | Future [Member]
Variable Interest Entity
Derivative, Notional Amount	$ 44,464