Derivative Instruments - Cumulative Hedging Adjustments and the Carrying Amount of Assets and Liabilities Designated in Fair Value Hedges (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Derivative Instruments, Gain (Loss) [Line Items]
Increase (decrease) in cumulative amount of basis adjustments	$ 304	$ 13
Available-for-sale investment securities
Derivative Instruments, Gain (Loss) [Line Items]
Carrying amount of the hedged assets	26,687	29,005
Cumulative hedging adjustment for hedged assets	257	(464)
Cumulative hedging adjustment asset related to discontinued hedging relationships	(8)	(72)
Carrying amount of assets related to discontinued hedging relationships	9,300	6,800
Amortized cost of the closed portfolios	20,800	17,500
Amortized cost of the closed portfolios designated as hedged	10,800	11,600
Increase (decrease) in cumulative amount of basis adjustments	293	13
Long-term debt
Derivative Instruments, Gain (Loss) [Line Items]
Carrying amount of the hedged liabilities	8,837	10,632
Cumulative hedging adjustment for hedged liabilities	209	39
Cumulative hedging adjustment liability related to discontinued hedging relationships	(75)	(149)
Carrying amount of liabilities related to discontinued hedging relationships	$ 16,100	$ 14,900