Significant Accounting Policies Consolidation (Details) $ in Thousands	3 Months Ended
	Dec. 31, 2017 USD ($)	Mar. 31, 2017	Dec. 31, 2016
Variable Interest Entity
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
Employee Owned Funds	2	1	1
Total Return Swap [Member]
Variable Interest Entity
Aggregate Counterparty Investment in ETF	$ 48,639
Derivative, Notional Amount	$ 51,066