Derivative Instruments - FV Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	$ 799	$ (507)	$ 2,152	$ 641
Net contractual interest income (expense) on interest-rate swaps	7,808	8,286	15,207	15,028
Interest income on mortgage loans	29,082	24,932	56,224	48,285
Long-term debt	(21,642)	(16,820)	(41,582)	(33,637)
Hedged asset, carrying amount	242,843		242,843		$ 174,080
Hedged asset, total basis adjustments	(443)		(443)		134
Hedged asset, discontinued fair value, remaining adjustments	(443)		(443)		134
Closed portfolio, amortized cost	70,938		70,938		56,786
Closed portfolio, designated UPB	5,649		5,649		4,389
Hedged liability, carrying amount	(76,004)		(76,004)		(72,174)
Hedged liability, total basis adjustments	3,468		3,468		1,281
Hedged liability, discontinued fair value, remaining adjustments	3,468		3,468		$ 1,281
Pay-fixed Swap
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	1,174	(695)	3,299	1,512
Receive-fixed Swap
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(1,106)	757	(3,366)	(1,098)
Basis Swap
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(63)	19	(131)	(27)
Foreign Currency Swap
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(36)	4	(60)	(4)
Pay-fixed Swaption
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	54	(58)	98	49
Receive-fixed Swaption
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(10)	30	(13)	(209)
Futures
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(1)	0	(1)	1
Risk Management Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(16)	64	(213)	220
Net contractual interest income (expense) on interest-rate swaps	(28)	7	(39)	(4)
Mortgage commitment derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	844	(553)	2,416	529
Credit enhancement derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(29)	(18)	(51)	(108)
Interest rate risk on held-for-investment mortgage loan | Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) in hedged item	(344)	106	(582)	70
Discontinued hedge related basis adjustment amortization	5	0	5	0
Change in unrealized gain (loss) in derivatives designated as hedging instruments	337	(106)	564	(70)
Interest accruals on hedging instruments	(9)	(5)	(17)	(5)
Total effect of fair value hedges	(11)	(5)	(30)	(5)
Interest rate risk on debt | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) in hedged item	748	(390)	2,371	805
Discontinued hedge related basis adjustment amortization	(119)	(21)	(184)	(34)
Change in unrealized gain (loss) in derivatives designated as hedging instruments	(568)	423	(2,092)	(791)
Interest accruals on hedging instruments	7	59	54	113
Total effect of fair value hedges	$ 68	$ 71	$ 149	$ 93