Derivative Instruments - Cumulative Hedging Adjustments and the Carrying Amount of Assets and Liabilities Designated in Fair Value Hedges (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Derivative Instruments, Gain (Loss) [Line Items]
Increase (decrease) in cumulative amount of basis adjustments	$ 314	$ 13
Available-for-sale investment securities
Derivative Instruments, Gain (Loss) [Line Items]
Carrying amount of the hedged assets	28,421	29,005
Cumulative hedging adjustment for hedged assets	281	(464)
Cumulative hedging adjustment asset related to discontinued hedging relationships	(47)	(72)
Carrying amount of assets related to discontinued hedging relationships	8,100	6,800
Amortized cost of the closed portfolios	21,000	17,500
Amortized cost of the closed portfolios designated as hedged	11,300	11,600
Increase (decrease) in cumulative amount of basis adjustments	302	13
Long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Carrying amount of the hedged liabilities	15,752	10,632
Cumulative hedging adjustment for hedged liabilities	217	39
Cumulative hedging adjustment liability related to discontinued hedging relationships	(98)	(149)
Carrying amount of liabilities related to discontinued hedging relationships	$ 11,600	$ 14,900