Investments of Operating Entities and Consolidated Funds - Securities borrowed and securities loaned (Details) - USD ($) $ in Thousands		Dec. 31, 2019	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Securities borrowed		$ 754,441	$ 407,795
Securities Borrowed, Offset Against Collateral, Net of Not Subject to Master Netting Arrangement, Policy Election	[1]	0	0
Securities borrowed, net amounts included on the condensed consolidated statements of financial condition		754,441	407,795
Securities borrowed, additional amounts, asset		0	0
Securities Borrowed, Collateral, Obligation to Return Cash	[2]	0	0
Securities Borrowed, Amount Offset Against Collateral		2,528	24,202
Securities borrowed, cash collateral pledged		0
Securities Loaned		1,601,866	414,852
Securities Loaned, Offset Against Collateral, Net of Not Subject to Master Netting Arrangement, Policy Election	[1]	0	0
Securities Loaned, Gross amounts recognized		1,601,866	414,852
Securities Loaned, Additional Amounts Available		0	0
Securities Loaned, Collateral, Right to Reclaim Cash	[2]	0	0
Securities Loaned, Amount Offset Against Collateral		16,830	23,542
Securities Sold under Agreements to Repurchase, Asset		23,244
Securities Loaned, Net amounts		(4,140)
Securities Sold under Agreements to Repurchase		23,244	0
Securities Sold under Agreements to Repurchase, Gross Including Not Subject to Master Netting Arrangement		0
Securities sold under agreements to repurchase, additional amounts		0
Securities Borrowed, Not Offset, Policy Election Deduction		751,913	383,593
Securities Loaned, Not Offset, Policy Election Deduction		$ 1,585,036	$ 391,310

[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.

[2] Includes the amount of cash collateral held/posted.