Debt (Pledged Assets Related to Secured Borrowings and Repurchase Agreement) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Pledged Assets related to secured borrowings [Line Items]
Total assets restricted as collateral	$ 67,458	$ 69,512
Secured debt	6,449	10,443
Amortized cost	28,114	28,416
Short-term borrowings	0	3,297
Asset Pledged as Collateral
Pledged Assets related to secured borrowings [Line Items]
Amortized cost	3,017	4,030
Pledged assets for Federal Home Loan Bank
Pledged Assets related to secured borrowings [Line Items]
Total assets restricted as collateral	27,600	27,900
Pledged assets for Federal Reserve Bank
Pledged Assets related to secured borrowings [Line Items]
Total assets restricted as collateral	33,900	34,000
Investment securities
Pledged Assets related to secured borrowings [Line Items]
Total assets restricted as collateral	3,165	4,036
Consumer \| Automotive
Pledged Assets related to secured borrowings [Line Items]
Total assets restricted as collateral	39,815	40,805
Consumer \| Consumer mortgage
Pledged Assets related to secured borrowings [Line Items]
Total assets restricted as collateral	18,478	18,703
Commercial
Pledged Assets related to secured borrowings [Line Items]
Total assets restricted as collateral	$ 6,000	$ 5,968

Amount of assets pledged to secure a debt instrument.

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Amortized cost excluding accrued interest, after allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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