Derivative Instruments - FV Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024	Dec. 31, 2024
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	$ (335)	$ 672
Net contractual interest income (expense) on interest-rate swaps	7,001	7,023
Interest income on mortgage loans	37,399	35,216
Long-term debt	(31,910)	(29,580)
Hedged asset, carrying amount	1,096,598		$ 1,109,445
Hedged asset, total basis adjustments	(364)		(816)
Hedged asset, discontinued fair value, remaining adjustments	(364)		(816)
Closed portfolio, amortized cost	161,901		813,536
Closed portfolio, designated UPB	21,033		26,825
Hedged liability, carrying amount	(45,051)		(47,849)
Hedged liability, total basis adjustments	2,952		3,390
Hedged liability, discontinued fair value, remaining adjustments	2,952		$ 3,390
Pay-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	(879)	1,362
Receive-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	1,015	(696)
Basis
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	12	1
Foreign currency
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	9	(8)
Pay-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	(14)	23
Receive-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	0	(4)
Futures
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	(1)	1
Risk Management Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	(76)	480
Net contractual interest income (expense) on interest-rate swaps	(218)	(199)
Mortgage commitment derivatives fair value gains (losses), net
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	(242)	207
Credit enhancement derivatives fair value gains (losses), net
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	(17)	(15)
Interest rate risk on held-for-investment mortgage loan | Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) in hedged item	436	(334)
Discontinued hedge related basis adjustment amortization	16	8
Change in unrealized gain (loss) in derivatives designated as hedging instruments	(441)	309
Interest accruals on hedging instruments	56	66
Total effect of fair value hedges	67	49
Interest rate risk on debt | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) in hedged item	(212)	428
Discontinued hedge related basis adjustment amortization	(226)	(206)
Change in unrealized gain (loss) in derivatives designated as hedging instruments	216	(355)
Interest accruals on hedging instruments	(23)	(167)
Total effect of fair value hedges	$ (245)	$ (300)