Allowance for Credit Losses - Schedule of Rollforward of Allowance for Credit Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 685	$ 670	$ 963
Charge-offs	(199)	(93)	(59)
Recoveries	29	34	57
Ending balance	773	$ 685	670
Accounting Standards Update [Extensible List]		Accounting Standards Update 2022-02
Loans and leases	61,292	$ 58,102
Accounting Standards Update 2022-02
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	(6)
Ending balance		(6)
Funded and Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	772	736
Ending balance	856	772	736
Funded Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan and lease losses	264	74	(291)
Unfunded Commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	87	66	85
Provision for loan and lease losses	(4)	21	(19)
Ending balance	83	87	66
Commercial | C&I
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	308	334	453
Charge-offs	(156)	(62)	(34)
Recoveries	14	9	21
Ending balance	339	308	334
Loans and leases	32,633	31,781
Commercial | C&I | Single Company
Allowance for Loan and Lease Losses [Roll Forward]
Charge-offs	(72)
Commercial | C&I | Paycheck Protection Plan
Allowance for Loan and Lease Losses [Roll Forward]
Loans and leases	29	76	1,000
Commercial | C&I | Accounting Standards Update 2022-02
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	1
Ending balance		1
Commercial | C&I | Funded and Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	363	380
Ending balance	388	363	380
Commercial | C&I | Funded Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan and lease losses	172	27	(106)
Commercial | C&I | Unfunded Commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	55	46	65
Provision for loan and lease losses	(6)	9	(19)
Ending balance	49	55	46
Commercial | Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	146	154	242
Charge-offs	(17)	(1)	(5)
Recoveries	2	1	5
Ending balance	172	146	154
Loans and leases	14,216	13,228
Commercial | Commercial Real Estate | Accounting Standards Update 2022-02
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	0
Ending balance		0
Commercial | Commercial Real Estate | Funded and Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	168	166
Ending balance	194	168	166
Commercial | Commercial Real Estate | Funded Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan and lease losses	41	(8)	(88)
Commercial | Commercial Real Estate | Unfunded Commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	22	12	10
Provision for loan and lease losses	0	10	2
Ending balance	22	22	12
Commercial | Credit card and other
Allowance for Loan and Lease Losses [Roll Forward]
Loans and leases	180	193
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Loans and leases	13,650	12,253
Consumer | Consumer real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	200	163	242
Charge-offs	(4)	(5)	(5)
Recoveries	9	19	27
Ending balance	233	200	163
Loans and leases	13,650	12,253
Consumer | Consumer real estate | Accounting Standards Update 2022-02
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	(7)
Ending balance		(7)
Consumer | Consumer real estate | Funded and Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	210	171
Ending balance	245	210	171
Consumer | Consumer real estate | Funded Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan and lease losses	35	23	(101)
Consumer | Consumer real estate | Unfunded Commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	10	8	10
Provision for loan and lease losses	2	2	(2)
Ending balance	12	10	8
Consumer | Credit card and other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	31	19	26
Charge-offs	(22)	(25)	(15)
Recoveries	4	5	4
Ending balance	29	31	19
Loans and leases	793	840
Consumer | Credit card and other | Accounting Standards Update 2022-02
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	0
Ending balance		0
Consumer | Credit card and other | Funded and Unfunded Loan Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	31	19
Ending balance	29	31	19
Consumer | Credit card and other | Funded Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Provision for loan and lease losses	16	32	4
Consumer | Credit card and other | Unfunded Commitment
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	0	0	0
Provision for loan and lease losses	0	0	0
Ending balance	$ 0	$ 0	$ 0