Loans and ACL - Summary of TDRs (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	$ 1,542	$ 1,525
ALLL attributable to TDRs	102	132
Performing TDRs
Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	1,390	1,361
Nonperforming TDRs
Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	152	164
Commercial: | Commercial and industrial | Performing TDRs
Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	147	138
Commercial: | CRE | Performing TDRs
Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	5	47
Consumer: | Residential mortgage | Performing TDRs
Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	692	648
Consumer: | Residential home equity and direct | Performing TDRs
Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	98	88
Consumer: | Indirect auto | Performing TDRs
Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	389	392
Consumer: | Indirect other | Performing TDRs
Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	7	6
Consumer: | Student | Performing TDRs
Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	25	5
Credit card | Performing TDRs
Financing Receivable [Line Items]
Financing Receivable, Troubled Debt Restructuring	$ 27	$ 37