Allowance for Credit Losses - Rollforward of Allowance for Credit Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	$ 773	$ 685	$ 670
Charge-offs	(157)	(199)	(93)
Recoveries	45	29	34
Provision for loan and lease losses	154	264	74
Ending balance	815	773	685
Off-Balance-Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	83	87	66
Provision for unfunded lending commitments	(4)	(4)	21
Ending balance	79	83	87
Allowance for credit losses	894	856	$ 772
Loans and leases	62,565	$ 61,292
Accounting Standards Update [Extensible List]		Accounting Standards Update 2023-02	Accounting Standards Update 2022-02
Accounting Standards Update 2022-02
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		$ (6)
Ending balance			$ (6)
Commercial | Commercial, financial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	339	308	334
Charge-offs	(77)	(156)	(62)
Recoveries	30	14	9
Provision for loan and lease losses	53	172	27
Ending balance	345	339	308
Off-Balance-Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	49	55	46
Provision for unfunded lending commitments	8	(6)	9
Ending balance	57	49	55
Allowance for credit losses	402	388	363
Loans and leases	33,428	32,633
Commercial | Commercial, financial and industrial | Single Company
Allowance for Loan and Lease Losses [Roll Forward]
Charge-offs		(72)
Commercial | Commercial, financial and industrial | Paycheck Protection Plan
Off-Balance-Sheet, Credit Loss, Liability [Roll Forward]
Loans and leases	12	29	76
Commercial | Commercial, financial and industrial | Accounting Standards Update 2022-02
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		1
Ending balance			1
Commercial | Commercial Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	172	146	154
Charge-offs	(56)	(17)	(1)
Recoveries	1	2	1
Provision for loan and lease losses	110	41	(8)
Ending balance	227	172	146
Off-Balance-Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	22	22	12
Provision for unfunded lending commitments	(11)	0	10
Ending balance	11	22	22
Allowance for credit losses	238	194	168
Loans and leases	14,421	14,216
Commercial | Commercial Real Estate | Accounting Standards Update 2022-02
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		0
Ending balance			0
Commercial | Credit card and other
Off-Balance-Sheet, Credit Loss, Liability [Roll Forward]
Loans and leases	174	180
Consumer
Off-Balance-Sheet, Credit Loss, Liability [Roll Forward]
Loans and leases	14,047	13,650
Consumer | Consumer real estate
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	233	200	163
Charge-offs	(3)	(4)	(5)
Recoveries	9	9	19
Provision for loan and lease losses	(18)	35	23
Ending balance	221	233	200
Off-Balance-Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	12	10	8
Provision for unfunded lending commitments	(1)	2	2
Ending balance	11	12	10
Allowance for credit losses	232	245	210
Loans and leases	14,047	13,650
Consumer | Consumer real estate | Accounting Standards Update 2022-02
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		(7)
Ending balance			(7)
Consumer | Credit card and other
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance	29	31	19
Charge-offs	(21)	(22)	(25)
Recoveries	5	4	5
Provision for loan and lease losses	9	16	32
Ending balance	22	29	31
Off-Balance-Sheet, Credit Loss, Liability [Roll Forward]
Beginning balance	0	0	0
Provision for unfunded lending commitments	0	0	0
Ending balance	0	0	0
Allowance for credit losses	22	29	31
Loans and leases	$ 669	793
Consumer | Credit card and other | Accounting Standards Update 2022-02
Allowance for Loan and Lease Losses [Roll Forward]
Beginning balance		$ 0
Ending balance			$ 0