Loans - Additional Information (Details) $ in Millions	3 Months Ended
Mar. 31, 2026 USD ($) segment	Mar. 31, 2025 USD ($)	Dec. 31, 2025 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Number of portfolio segments \| segment	3
Accrued interest receivable	$ 3,000		$ 3,100
Financing receivable, nonaccrual, interest income	4	$ 3
Net loans held for investment	424,124		430,213
Federal Home Loan banks
Financing Receivable, Allowance for Credit Loss [Line Items]
Net loans held for investment	6,200		6,600
Remaining borrowing capacity	34,500		34,400
Federal Reserve Discount Window
Financing Receivable, Allowance for Credit Loss [Line Items]
Net loans held for investment	87,400		91,600
Remaining borrowing capacity	49,900		$ 53,300
Domestic credit card: \| Domestic Credit Card and Commercial Banking Portfolios
Financing Receivable, Allowance for Credit Loss [Line Items]
Revolving loans converted to term during period	$ 407	$ 141

Amount, before allowance for credit loss, of accrued interest on financing receivable.

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