Loans and Related Allowance for Credit Losses (Financial Impact and TDRs by Concession Type) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) loan	Dec. 31, 2020 USD ($) loan	Dec. 31, 2019 USD ($) loan
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	6,166	12,343	14,623
Pre-TDR Amortized Cost Basis	$ 644	$ 691
Post-TDR Amortized Cost Basis	613	602
Pre-TDR Recorded Investment			$ 450
Post-TDR Recorded Investment			413
Principal Forgiveness
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post-TDR Amortized Cost Basis	6	39
Post-TDR Recorded Investment
Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post-TDR Amortized Cost Basis	64	144
Post-TDR Recorded Investment			108
Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post-TDR Amortized Cost Basis	$ 543	$ 419
Post-TDR Recorded Investment			$ 305
Commercial
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	57	73	75
Pre-TDR Amortized Cost Basis	$ 536	$ 513
Post-TDR Amortized Cost Basis	516	441
Pre-TDR Recorded Investment			$ 278
Post-TDR Recorded Investment			252
Commercial | Principal Forgiveness
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post-TDR Amortized Cost Basis	6	39
Commercial | Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post-TDR Amortized Cost Basis		56
Post-TDR Recorded Investment			11
Commercial | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post-TDR Amortized Cost Basis	$ 510	$ 346
Post-TDR Recorded Investment			$ 241
Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Number of Loans | loan	6,109	12,270	14,548
Pre-TDR Amortized Cost Basis	$ 108	$ 178
Post-TDR Amortized Cost Basis	97	161
Pre-TDR Recorded Investment			$ 172
Post-TDR Recorded Investment			161
Consumer | Rate Reduction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post-TDR Amortized Cost Basis	64	88
Post-TDR Recorded Investment			97
Consumer | Other
Financing Receivable, Troubled Debt Restructuring [Line Items]
Post-TDR Amortized Cost Basis	$ 33	$ 73
Post-TDR Recorded Investment			$ 64