Loans and Related Allowance for Credit Losses (Modified, Amortized Cost Basis) (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2023 USD ($)	Sep. 30, 2023 USD ($)
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 904	$ 1,946
% of Loan Class	0.28%	0.61%
Unfunded lending related commitments	$ 300	$ 300
Interest Rate Reduction
Financing Receivable [Line Items]
Amortized cost basis, modified	16	16
Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	664	1,452
Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	105	196
Repayment Plan
Financing Receivable [Line Items]
Amortized cost basis, modified	21	46
Interest Rate Reduction and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified		10
Payment Delay and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	7	20
Other
Financing Receivable [Line Items]
Amortized cost basis, modified	91	206
Total commercial
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 821	$ 1,782
% of Loan Class	0.38%	0.82%
Total commercial | Interest Rate Reduction
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 15	$ 15
Total commercial | Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	663	1,449
Total commercial | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	53	107
Total commercial | Payment Delay and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	7	20
Total commercial | Other
Financing Receivable [Line Items]
Amortized cost basis, modified	83	191
Total commercial | Commercial and industrial
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 498	$ 960
% of Loan Class	0.29%	0.55%
Total commercial | Commercial and industrial | Interest Rate Reduction
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 15	$ 15
Total commercial | Commercial and industrial | Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	356	704
Total commercial | Commercial and industrial | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	37	91
Total commercial | Commercial and industrial | Payment Delay and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	7	20
Total commercial | Commercial and industrial | Other
Financing Receivable [Line Items]
Amortized cost basis, modified	83	130
Total commercial | Commercial real estate
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 323	$ 822
% of Loan Class	0.90%	2.30%
Total commercial | Commercial real estate | Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 307	$ 745
Total commercial | Commercial real estate | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	16	16
Total commercial | Commercial real estate | Other
Financing Receivable [Line Items]
Amortized cost basis, modified		61
Total consumer
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 83	$ 164
% of Loan Class	0.08%	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	3
Total consumer | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	52	89
Total consumer | Repayment Plan
Financing Receivable [Line Items]
Amortized cost basis, modified	21	46
Total consumer | Interest Rate Reduction and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified		10
Total consumer | Other
Financing Receivable [Line Items]
Amortized cost basis, modified	8	15
Total consumer | Residential real estate
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 54	$ 93
% of Loan Class	0.11%	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 | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	50	83
Total consumer | Residential real estate | Interest Rate Reduction and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified		3
Total consumer | Residential real estate | Other
Financing Receivable [Line Items]
Amortized cost basis, modified	3	6
Total consumer | Home equity
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 7	$ 22
% of Loan Class	0.03%	0.08%
Total consumer | Home equity | Payment Delay
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 2	$ 6
Total consumer | Home equity | Interest Rate Reduction and Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified		7
Total consumer | Home equity | Other
Financing Receivable [Line Items]
Amortized cost basis, modified	5	9
Total consumer | Credit card
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 20	$ 45
% of Loan Class	0.28%	0.64%
Total consumer | Credit card | Repayment Plan
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 20	$ 45
Total consumer | Education
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 1	$ 3
% of Loan Class	0.05%	0.15%
Total consumer | Education | Term Extension
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 1	$ 3
Total consumer | Other consumer
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 1	$ 1
% of Loan Class	0.02%	0.02%
Total consumer | Other consumer | Repayment Plan
Financing Receivable [Line Items]
Amortized cost basis, modified	$ 1	$ 1