Investments of Operating Entities and Consolidated Funds - Other Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2019		Dec. 31, 2018
Investment Holdings [Line Items]
Other investments	$ 200,297		$ 181,407
Portfolio Funds, Consolidated Funds	177,828		186,395
Portfolio Funds, at fair value
Investment Holdings [Line Items]
Other investments	146,133	[1]	141,236	[2]
Equity Method Investments
Investment Holdings [Line Items]
Other investments	54,164		40,171
Enterprise LP [Member]
Investment Holdings [Line Items]
Portfolio Funds, Consolidated Funds	99,493		97,656
Merger Fund [Member]
Investment Holdings [Line Items]
Portfolio Funds, Consolidated Funds	$ 78,335		$ 88,739

[1] In accordance with US GAAP, certain investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition.

[2] In accordance with US GAAP, certain investments that are measured at fair value using the net asset value per share (or its equivalent) as a practical expedient have not been classified in the fair value hierarchy. The fair value amounts presented in this table are intended to permit reconciliation of the fair value hierarchy to the amounts presented in the condensed consolidated statement of financial condition.