Derivative Instruments - FV Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	$ 975	$ 799	$ 637	$ 2,152
Net contractual interest expense on interest-rate swaps	7,035	7,808	13,821	15,207
Interest income on mortgage loans	32,655	29,082	64,792	56,224
Long-term debt	(27,122)	(21,642)	(53,787)	(41,582)
Hedged asset, carrying amount	356,930		356,930		$ 293,788
Hedged asset, total basis adjustments	(575)		(575)		(628)
Hedged asset, discontinued fair value, remaining adjustments	(575)		(575)		(628)
Closed portfolio, amortized cost	171,706		171,706		98,377
Closed portfolio, designated UPB	3,186		3,186		5,187
Hedged liability, carrying amount	(70,459)		(70,459)		(73,790)
Hedged liability, total basis adjustments	4,747		4,747		4,713
Hedged liability, discontinued fair value, remaining adjustments	4,747		4,747		$ 4,713
Pay-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	1,858	1,174	268	3,299
Receive-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(1,010)	(1,106)	562	(3,366)
Basis
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	15	(63)	28	(131)
Foreign currency
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	2	(36)	10	(60)
Pay-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	12	54	(21)	98
Receive-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(2)	(10)	(3)	(13)
Futures
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	1	(1)	1	(1)
Risk Management Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	748	(16)	539	(213)
Net contractual interest expense on interest-rate swaps	(128)	(28)	(306)	(39)
Mortgage commitment derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	198	844	84	2,416
Credit enhancement derivatives fair value gains (losses), net
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	29	(29)	14	(51)
Interest rate risk on held-for-investment mortgage loan | Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) in hedged item	(144)	(344)	33	(582)
Discontinued hedge related basis adjustment amortization	9	5	20	5
Change in unrealized gain (loss) in derivatives designated as hedging instruments	132	337	(82)	564
Interest accruals on hedging instruments	27	(9)	53	(17)
Total effect of fair value hedges	24	(11)	24	(30)
Interest rate risk on debt | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) in hedged item	669	748	430	2,371
Discontinued hedge related basis adjustment amortization	(199)	(119)	(395)	(184)
Change in unrealized gain (loss) in derivatives designated as hedging instruments	(503)	(568)	(71)	(2,092)
Interest accruals on hedging instruments	(293)	7	(522)	54
Total effect of fair value hedges	$ (326)	$ 68	$ (558)	$ 149