Derivative Instruments - FV Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	$ 1,009	$ 13	$ 3,161	$ 654
Net contractual interest expense on interest-rate swaps	7,124	6,972	22,331	22,000
Interest income on mortgage loans	30,114	24,798	86,338	73,083
Long-term debt	(23,709)	(18,009)	(65,291)	(51,646)
Hedged asset, carrying amount	253,002		253,002		$ 174,080
Hedged asset, total basis adjustments	(719)		(719)		134
Hedged asset, discontinued fair value, remaining adjustments	(719)		(719)		134
Closed portfolio, amortized cost	59,031		59,031		56,786
Closed portfolio, designated UPB	5,595		5,595		4,389
Hedged liability, carrying amount	(73,711)		(73,711)		(72,174)
Hedged liability, total basis adjustments	4,777		4,777		1,281
Hedged liability, discontinued fair value, remaining adjustments	4,777		4,777		$ 1,281
Pay-fixed Swap
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	2,510	343	5,809	1,855
Receive-fixed Swap
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(1,903)	(209)	(5,269)	(1,307)
Basis Swap
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	5	(12)	(126)	(39)
Foreign Currency Swap
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(62)	(19)	(122)	(23)
Pay-fixed Swaption
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	43	6	141	55
Receive-fixed Swaption
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(6)	(14)	(19)	(223)
Futures
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	0	0	(1)	1
Risk Management Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	524	93	311	313
Net contractual interest expense on interest-rate swaps	(63)	(2)	(102)	(6)
Mortgage commitment derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	517	(25)	2,933	504
Credit enhancement derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(32)	(55)	(83)	(163)
Interest rate risk on held-for-investment mortgage loan | Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) in hedged item	(285)	(1)	(867)	69
Discontinued hedge related basis adjustment amortization	9	(3)	14	(3)
Change in unrealized gain (loss) in derivatives designated as hedging instruments	269	(1)	833	(71)
Interest accruals on hedging instruments	7	(4)	(10)	(9)
Total effect of fair value hedges	0	(9)	(30)	(14)
Interest rate risk on debt | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) in hedged item	1,477	195	3,848	1,000
Discontinued hedge related basis adjustment amortization	(145)	(20)	(329)	(54)
Change in unrealized gain (loss) in derivatives designated as hedging instruments	(1,289)	(191)	(3,381)	(982)
Interest accruals on hedging instruments	(108)	65	(54)	178
Total effect of fair value hedges	$ (65)	$ 49	$ 84	$ 142