Derivatives - Derivative Gains and Losses (Details) - Not Designated as Hedging Instrument, Economic Hedge - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	$ 554	$ (526)
Gain (Loss) on Derivative Instruments \| Interest-rate management derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	383	(573)
Gain (Loss) on Derivative Instruments \| Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	303	(317)
Gain (Loss) on Derivative Instruments \| Written options \| Written
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(6)	126
Gain (Loss) on Derivative Instruments \| Purchased options \| Purchased
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	15	(216)
Gain (Loss) on Derivative Instruments \| Futures
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	71	(166)
Gain (Loss) on Derivative Instruments \| Mortgage commitment derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	222	(108)
Gain (Loss) on Derivative Instruments \| CRT-Related Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	32	44
Gain (Loss) on Derivative Instruments \| Other
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	$ (83)	$ 111