Occupancy Expense and Information Systems and Communications Expense - Summary of Lease Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Finance lease:
Amortization of right-of-use assets	$ 27	$ 20
Interest on lease liabilities	6	9
Total finance lease expense	33	29
Sublease income	(11)	(11)
Net finance lease expense	22	18
Operating lease:
Operating lease expense	147	169
Sublease income	(18)	(16)
Net operating lease expense	129	153
Net lease expense	151	171
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from finance leases	6	9
Operating cash flows from operating leases	198	192
Financing cash flows from finance leases	47	33
Right-of-use assets obtained in exchange for new lease obligations:
Operating leases	69	38
Finance leases	$ 108	$ 0