Derivative Instruments - Cumulative Hedging Adjustments and the Carrying Amount of Assets and Liabilities Designated in Fair Value Hedges (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Increase (decrease) in cumulative amount of basis adjustments	$ 88	$ 335
Available-for-sale investment securities
Derivative Instruments, Gain (Loss) [Line Items]
Carrying amount of the hedged assets	18,981	23,924
Cumulative hedging adjustment for hedged assets	(474)	(93)
Cumulative hedging adjustment asset related to discontinued hedging relationships	(108)	(18)
Carrying amount of assets related to discontinued hedging relationships	7,100	830
Amortized cost of the closed portfolios	15,400	15,600
Amortized cost of the closed portfolios designated as hedged	9,500	9,600
Increase (decrease) in cumulative amount of basis adjustments	88	335
Long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Carrying amount of the hedged liabilities	13,683	12,034
Cumulative hedging adjustment for hedged liabilities	(97)	(32)
Cumulative hedging adjustment liability related to discontinued hedging relationships	(110)	(116)
Carrying amount of liabilities related to discontinued hedging relationships	$ 6,700	$ 7,200