Occupancy Expense and Information Systems and Communications Expense - Lease Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Leases [Abstract]
Operating Lease, Lease Income, Statement of Income or Comprehensive Income [Extensible Enumeration]	Occupancy	Occupancy
Amortization of right-of-use assets	$ 48	$ 48
Interest on lease liabilities	3	5
Total finance lease expense	51	53
Sublease income	0	0
Net finance lease expense	51	53
Operating lease expense	168	163
Sublease income	(17)	(23)
Net operating lease expense	151	140
Net lease expense	202	193
Operating cash flows from finance leases	3	5
Operating cash flows from operating leases	179	197
Financing cash flows from finance leases	46	45
Operating leases	174	461
Finance leases	$ 0	$ 0