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