Derivative Instruments - FV Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	$ 312	$ 975	$ 984	$ 637
Net contractual interest income (expense) on interest-rate swaps	7,268	7,035	14,291	13,821
Interest income on mortgage loans	35,617	32,655	70,833	64,792
Long-term debt	(29,877)	(27,122)	(59,457)	(53,787)
Hedged asset, carrying amount	854,132		854,132		$ 449,137
Hedged asset, total basis adjustments	(510)		(510)		(174)
Hedged asset, discontinued fair value, remaining adjustments	(510)		(510)		(174)
Closed portfolio, amortized cost	497,361		497,361		218,419
Closed portfolio, designated UPB	13,602		13,602		9,955
Hedged liability, carrying amount	(56,889)		(56,889)		(59,462)
Hedged liability, total basis adjustments	3,880		3,880		3,751
Hedged liability, discontinued fair value, remaining adjustments	3,880		3,880		$ 3,751
Pay-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	237	1,858	1,599	268
Receive-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	209	(1,010)	(487)	562
Basis
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	(4)	15	(3)	28
Foreign currency
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	(3)	2	(11)	10
Pay-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	21	12	44	(21)
Receive-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	7	(2)	3	(3)
Futures
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	1	1	2	1
Risk Management Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	217	748	697	539
Net contractual interest income (expense) on interest-rate swaps	(251)	(128)	(450)	(306)
Mortgage commitment derivatives fair value gains (losses), net
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	94	198	301	84
Credit enhancement derivatives fair value gains (losses), net
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	1	29	(14)	14
Interest rate risk on held-for-investment mortgage loan | Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) in hedged item	(28)	(144)	(362)	33
Discontinued hedge related basis adjustment amortization	18	9	26	20
Change in unrealized gain (loss) in derivatives designated as hedging instruments	6	132	315	(82)
Interest accruals on hedging instruments	76	27	142	53
Total effect of fair value hedges	72	24	121	24
Interest rate risk on debt | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) in hedged item	129	669	557	430
Discontinued hedge related basis adjustment amortization	(222)	(199)	(428)	(395)
Change in unrealized gain (loss) in derivatives designated as hedging instruments	(78)	(503)	(433)	(71)
Interest accruals on hedging instruments	(113)	(293)	(280)	(522)
Total effect of fair value hedges	$ (284)	$ (326)	$ (584)	$ (558)