Leases - Leases included in the Condensed Consolidated Statement of Financial Condition (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease right-of-use assets	$ 337,933	$ 360,185
Operating lease liabilities	438,854	465,907
Property and equipment, gross	5,167	3,825
Amortization of right-of-use assets	(1,440)	(1,317)
Property and equipment, net	3,727	2,508
Finance lease liabilities	$ 3,736	$ 2,544