Derivatives - Derivative Gains and Losses (Details) - Not Designated as Hedging Instrument, Economic Hedge - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	$ (317)	$ (1,370)	$ (1,050)	$ (263)
Gain (Loss) on Derivative Instruments \| Interest-rate management derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(157)	(1,188)	(885)	2
Gain (Loss) on Derivative Instruments \| Swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	108	(425)	(307)	(27)
Gain (Loss) on Derivative Instruments \| Written options \| Written
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	127	223	347	174
Gain (Loss) on Derivative Instruments \| Purchased options \| Purchased
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(372)	(511)	(729)	(213)
Gain (Loss) on Derivative Instruments \| Futures
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(20)	(475)	(196)	68
Gain (Loss) on Derivative Instruments \| Mortgage commitment derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	(239)	(415)	(422)	(343)
Gain (Loss) on Derivative Instruments \| CRT-Related Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	10	39	26	47
Gain (Loss) on Derivative Instruments \| Other
Derivative Instruments, Gain (Loss) [Line Items]
Derivative gains (losses)	$ 69	$ 194	$ 231	$ 31