Loans and Allowance for Credit Losses - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged at the Federal Home Loan Bank	$ 368,584		$ 368,584		$ 366,456
Loans pledged at the Federal Reserve Bank	83,200		83,200		82,800
Net unearned interest and deferred fees and costs on originated loans and unamortized premiums and discounts on purchased loans	$ 2,700		$ 2,700		2,700
Reasonable and supportable period for allowance for credit loss	3 years		3 years
Foreclosed residential real estate property included in other real estate owned	$ 23		$ 23		26
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	49		49		47
Residential mortgage loans secured by residential real estate in process of foreclosure	605		605		728
Modified loans	1,631	$ 1,123	2,848	$ 1,879
Commitments to lend	$ 371		371
Trial Modifications
Accounts, Notes, Loans and Financing Receivable [Line Items]
Modified loans			$ 43
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	$ 379		$ 379		487
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	$ 116	$ 91	$ 228	$ 174
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	$ 125,500		$ 125,500		$ 123,100