Loans and Allowance for Credit Losses - Loans by Portfolio Class, Including Delinquency Status (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 380,243		$ 380,243		$ 379,832
Loans purchased from GNMA mortgage pools
Financing Receivable, Recorded Investment, Past Due [Line Items]
Interest income on nonperforming loans	6	$ 6	10	$ 11
Nonperforming
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,637		1,637		1,793
Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	376,487		376,487		375,950
30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	1,153		1,153		1,279
90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	966		966		810
Commercial | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	147,416		147,416		139,484
Commercial | Commercial | Nonperforming
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	575		575		670
Commercial | Commercial | Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	146,424		146,424		138,362
Commercial | Commercial | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	325		325		356
Commercial | Commercial | 90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	92		92		96
Commercial | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	48,181		48,181		48,859
Commercial | Commercial real estate | Nonperforming
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	763		763		824
Commercial | Commercial real estate | Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	47,172		47,172		47,948
Commercial | Commercial real estate | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	113		113		78
Commercial | Commercial real estate | 90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	133		133		9
Consumer | Residential mortgages
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	114,475		114,475		118,813
Consumer | Residential mortgages | Loans purchased from GNMA mortgage pools
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans 30-89 days past due purchased from Government National Mortgage Association mortgage pools, classified as current	558		558		660
Loans 90 days or more past due purchased from Government National Mortgage Association mortgage pools, classified as current	2,200		2,200		2,300
Consumer | Residential mortgages | Nonperforming
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	145		145		152
Consumer | Residential mortgages | Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	113,841		113,841		118,267
Consumer | Residential mortgages | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	171		171		188
Consumer | Residential mortgages | 90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	318		318		206
Consumer | Credit card
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	30,023		30,023		30,350
Consumer | Credit card | Nonperforming
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	0		0		0
Consumer | Credit card | Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	29,280		29,280		29,487
Consumer | Credit card | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	371		371		428
Consumer | Credit card | 90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	372		372		435
Consumer | Other retail
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	40,148		40,148		42,326
Consumer | Other retail | Nonperforming
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	154		154		147
Consumer | Other retail | Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	39,770		39,770		41,886
Consumer | Other retail | 30-89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	173		173		229
Consumer | Other retail | 90 Days or More Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total loans	$ 51		$ 51		$ 64