Occupancy Expense and Information Systems and Communications Expense - Lease Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Leases [Abstract]
Amortization of right-of-use assets	$ 48	$ 50
Interest on lease liabilities	5	6
Total finance lease expense	53	56
Sublease income	0	(10)
Net finance lease expense	53	46
Operating lease expense	$ 163	$ 130
Operating Lease, Lease Income, Statement of Income or Comprehensive Income [Extensible Enumeration]	Occupancy	Occupancy
Sublease income	$ (23)	$ (16)
Net operating lease expense	140	114
Net lease expense	193	160
Operating cash flows from finance leases	5	6
Operating cash flows from operating leases	197	161
Financing cash flows from finance leases	45	58
Operating leases	461	88
Finance leases	$ 0	$ 99