Occupancy Expense and Information Systems and Communications Expense - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Expenses [Line Items]
Depreciation and amortization		$ 829	$ 842	$ 859
Sale and leaseback transaction, gain (loss), net	$ 11
Sale leaseback transaction lease term	3 years
Finance lease right-of-use asset	$ 167	119	167
Finance lease liability	$ 176	$ 130	$ 176
Finance Lease, Liability, Statement of Financial Position [Extensible Enumeration]	Long-term debt	Long-term debt	Long-term debt
Finance lease, right-of-use asset, accumulated amortization		$ 88
Interest on lease liabilities		5	$ 6
Right-of-use assets	$ 500	$ 805	$ 500
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other assets	Other assets	Other assets
Lease liabilities		$ 832
Operating Lease, Liability, Statement of Financial Position [Extensible List]		Accrued expenses and other liabilities
Operating leases not yet commenced		$ 145
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Premises and equipment (net of accumulated depreciation of $6,062 and $5,745)	Premises and equipment (net of accumulated depreciation of $6,062 and $5,745)	Premises and equipment (net of accumulated depreciation of $6,062 and $5,745)
Minimum
Expenses [Line Items]
Operating leases not yet commenced, lease terms		6 years
Maximum
Expenses [Line Items]
Operating leases not yet commenced, lease terms		12 years
Sale Leaseback of Two Properties in United States in 2022
Expenses [Line Items]
Proceeds from sale of productive assets	$ 27