Loans and Related Allowance for Credit Losses (Modified, Amortized Cost Basis) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 829	$ 904	$ 2,686	$ 1,946
% of Loan Class	0.26%	0.28%	0.84%	0.61%
Unfunded lending related commitments	$ 500	$ 300	$ 500	$ 300
Interest Rate Reduction
Financing Receivable [Line Items]
Amortized cost basis, modified		16	27	16
Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	626	664	1,858	1,452
Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	137	105	212	196
Repayment Plan
Financing Receivable [Line Items]
Amortized cost basis, modified	22	21	58	53
Payment Delay and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	6	7	304	20
Interest Rate Reduction and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	12		107	3
Interest Rate Reduction and Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified			15
Other
Financing Receivable [Line Items]
Amortized cost basis, modified	26	91	105	206
Commercial and industrial | Interest Rate Reduction
Financing Receivable [Line Items]
Amortized cost basis, modified	11	15	146	15
Commercial and industrial | Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	389	363	1,188	724
Commercial and industrial | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	25	44	206	111
Commercial real estate | Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	253	307	1,073	745
Commercial real estate | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	87	16	248	16
Residential real estate | Interest Rate Reduction
Financing Receivable [Line Items]
Amortized cost basis, modified	1	1	3	4
Residential real estate | Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	1		4	3
Residential real estate | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	28	50	67	83
Home equity | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	3	2	10	6
Education | Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	1	1	4	3
Total commercial
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 764	$ 821	$ 2,523	$ 1,782
% of Loan Class	0.35%	0.38%	1.14%	0.82%
Total commercial | Interest Rate Reduction
Financing Receivable [Line Items]
Amortized cost basis, modified		$ 15	$ 27	$ 15
Total commercial | Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 625	663	1,853	1,449
Total commercial | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	106	53	135	107
Total commercial | Payment Delay and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	6	7	304	20
Total commercial | Interest Rate Reduction and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	11		104
Total commercial | Interest Rate Reduction and Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified			15
Total commercial | Other
Financing Receivable [Line Items]
Amortized cost basis, modified	16	83	85	191
Total commercial | Commercial and industrial
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 410	$ 498	$ 1,349	$ 960
% of Loan Class	0.23%	0.29%	0.75%	0.55%
Total commercial | Commercial and industrial | Interest Rate Reduction
Financing Receivable [Line Items]
Amortized cost basis, modified		$ 15	$ 27	$ 15
Total commercial | Commercial and industrial | Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 372	356	927	704
Total commercial | Commercial and industrial | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	19	37	34	91
Total commercial | Commercial and industrial | Payment Delay and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	6	7	157	20
Total commercial | Commercial and industrial | Interest Rate Reduction and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	11		104
Total commercial | Commercial and industrial | Interest Rate Reduction and Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified			15
Total commercial | Commercial and industrial | Other
Financing Receivable [Line Items]
Amortized cost basis, modified	2	83	85	130
Total commercial | Commercial real estate
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 354	$ 323	$ 1,174	$ 822
% of Loan Class	1.01%	0.90%	3.34%	2.30%
Total commercial | Commercial real estate | Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 253	$ 307	$ 926	$ 745
Total commercial | Commercial real estate | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	87	16	101	16
Total commercial | Commercial real estate | Payment Delay and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified			147
Total commercial | Commercial real estate | Other
Financing Receivable [Line Items]
Amortized cost basis, modified	14			61
Total consumer
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 65	$ 83	$ 163	$ 164
% of Loan Class	0.06%	0.08%	0.16%	0.16%
Total consumer | Interest Rate Reduction
Financing Receivable [Line Items]
Amortized cost basis, modified		$ 1		$ 1
Total consumer | Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 1	1	$ 5	3
Total consumer | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	31	52	77	89
Total consumer | Repayment Plan
Financing Receivable [Line Items]
Amortized cost basis, modified	22	21	58	53
Total consumer | Interest Rate Reduction and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	1		3	3
Total consumer | Other
Financing Receivable [Line Items]
Amortized cost basis, modified	10	8	20	15
Total consumer | Residential real estate
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 33	$ 54	$ 79	$ 93
% of Loan Class	0.07%	0.11%	0.17%	0.20%
Total consumer | Residential real estate | Interest Rate Reduction
Financing Receivable [Line Items]
Amortized cost basis, modified		$ 1		$ 1
Total consumer | Residential real estate | Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified			$ 1
Total consumer | Residential real estate | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 28	50	67	83
Total consumer | Residential real estate | Interest Rate Reduction and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	1		3	3
Total consumer | Residential real estate | Other
Financing Receivable [Line Items]
Amortized cost basis, modified	4	3	8	6
Total consumer | Home equity
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 10	$ 7	$ 27	$ 22
% of Loan Class	0.04%	0.03%	0.10%	0.08%
Total consumer | Home equity | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 3	$ 2	$ 10	$ 6
Total consumer | Home equity | Repayment Plan
Financing Receivable [Line Items]
Amortized cost basis, modified	1		5	7
Total consumer | Home equity | Other
Financing Receivable [Line Items]
Amortized cost basis, modified	6	5	12	9
Total consumer | Credit card
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 21	$ 20	$ 52	$ 45
% of Loan Class	0.31%	0.28%	0.76%	0.64%
Total consumer | Credit card | Repayment Plan
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 21	$ 20	$ 52	$ 45
Total consumer | Education
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 1	$ 1	$ 4	$ 3
% of Loan Class	0.06%	0.05%	0.24%	0.15%
Total consumer | Education | Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 1	$ 1	$ 4	$ 3
Total consumer | Other consumer
Financing Receivable [Line Items]
Amortized cost basis, modified		$ 1	$ 1	$ 1
% of Loan Class		0.02%	0.02%	0.02%
Total consumer | Other consumer | Repayment Plan
Financing Receivable [Line Items]
Amortized cost basis, modified		$ 1	$ 1	$ 1