Leases - Leases included in the Condensed Consolidated Statement of Financial Condition (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019
Leases [Abstract]
Operating lease right-of-use assets	$ 419,247	$ 438,700
Operating lease liabilities	539,096	574,500
Property and equipment, gross	2,356
Accumulated depreciation	(286)
Property and equipment, net	2,070	2,400
Finance lease liabilities	$ 2,074	$ 2,400