Investments of Operating Entities and Consolidated Funds - Securities borrowed and securities loaned (Details) - USD ($) $ in Thousands		Jun. 30, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Securities Borrowed, Gross		$ 1,390,366	$ 407,795
Securities borrowed, gross amounts offset on the condensed consolidated statements of financial condition	[1]	0	0
Securities borrowed, net amounts included on the condensed consolidated statements of financial condition		1,390,366	407,795
Securities borrowed, additional amounts, asset		0	0
Securities borrowed, financial instruments		1,343,751	383,593
Securities borrowed, cash collateral pledged		0	0
Securities borrowed, net amounts		46,615	24,202
Securities Loaned, Gross		1,492,986	414,852
Securities Loaned, Gross amounts offset on the Condensed Consolidated Statements of Financial Condition	[1]	0	0
Securities Loaned, Gross amounts recognized		1,492,986	414,852
Securities Loaned, Additional Amounts Available		0	0
Securities Loaned, Financial instruments		1,445,362	391,310
Securities Loaned, Net amounts		$ 47,624	$ 23,542

[1] Includes financial instruments subject to enforceable master netting provisions that are permitted to be offset to the extent an event of default has occurred.