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Loans - Additional Information (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) segment	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Financing Receivable, Allowance for Credit Loss [Line Items]
Number of portfolio segments | segment			3
Accrued interest receivable	$ 2,200		$ 2,200		$ 2,200
Net loans held for investment	303,709		303,709		305,176
Federal Home Loan banks
Financing Receivable, Allowance for Credit Loss [Line Items]
Net loans held for investment	7,200		7,200		7,400
Remaining borrowing capacity	37,000		37,000		32,100
Federal Reserve Discount Window
Financing Receivable, Allowance for Credit Loss [Line Items]
Net loans held for investment	82,400		82,400		78,300
Remaining borrowing capacity	46,900		46,900		$ 41,400
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	$ 267	$ 101	$ 588	$ 443

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

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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