Loans and Allowance for Credit Losses - Additional Information (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
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged at the Federal Home Loan Bank	$ 372,706		$ 372,706		$ 372,249
Loans pledged at the Federal Reserve Bank	90,300		90,300		85,100
Net unearned interest and deferred fees and costs on originated loans and unamortized premiums and discounts on purchased loans	$ 2,100		$ 2,100		2,500
Reasonable and supportable period for allowance for credit loss	3 years		3 years
Foreclosed residential real estate property included in other real estate owned	$ 21		$ 21		21
Foreclosed residential real estate related to mortgage loans whose payments are insured by the Federal Housing Administration or guaranteed by the United States Department of Veterans Affairs	55		55		46
Residential mortgage loans secured by residential real estate in process of foreclosure	553		553		576
Modified loans	1,468	$ 1,631	2,686	$ 2,848
Commitments to lend	$ 438		438
Trial Modifications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Modified loans			$ 173
Credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification amortization period	60 months		60 months
GNMA loans upon foreclosure
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential mortgage loans secured by residential real estate in process of foreclosure	$ 340		$ 340		354
Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan threshold when individually evaluated for allowance calculation	$ 5		$ 5
Threshold period to be placed on nonaccrual status	90 days		90 days
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan modification amortization period	60 months		60 months
Consumer | Residential Mortgages and Other Retail Loans Secured by 1-4 Family Properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period for charge-off to fair value of collateral less costs to sell	180 days		180 days
Consumer | Residential Mortgages Loans and Junior Liens Secured by 1-4 Family Properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period to be placed on nonaccrual status	120 days		120 days
Consumer | First Lien
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period to be placed on nonaccrual status	180 days		180 days
Consumer | Credit card
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due for charge-off	180 days		180 days
Modified loans	$ 123	$ 116	$ 244	$ 228
Consumer | Other Retail Loans not Secured by 1-4 Family Properties
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due for charge-off	120 days		120 days
Consumer | Revolving Consumer Lines
Accounts, Notes, Loans and Financing Receivable [Line Items]
Threshold period past due for charge-off	180 days		180 days
Federal Home Loan Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged at the Federal Home Loan Bank	$ 128,800		$ 128,800		$ 127,600