Leases - Leases included in the Condensed Consolidated Statement of Financial Condition (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019
Leases [Abstract]
Operating lease right-of-use assets	$ 378,083	$ 438,700
Operating lease liabilities	488,592	574,500
Property and equipment, gross	3,436
Accumulated depreciation	(932)
Property and equipment, net	2,504	2,400
Finance lease liabilities	$ 2,535	$ 2,400