Leases - Leases included in the Condensed Consolidated Statement of Financial Condition (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Jan. 01, 2019
Leases [Abstract]
Operating lease right-of-use assets	$ 397,187	$ 438,700
Operating lease liabilities	513,875	574,500
Property and equipment, gross	2,356
Accumulated depreciation	(577)
Property and equipment, net	1,779	2,400
Finance lease liabilities	$ 1,789	$ 2,400