Derivative Instruments - FV Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	$ 803	$ 1,009	$ 1,440	$ 3,161
Net contractual interest expense on interest-rate swaps	7,220	7,124	21,041	22,331
Interest income on mortgage loans	33,711	30,114	98,503	86,338
Long-term debt	(27,994)	(23,709)	(81,781)	(65,291)
Hedged asset, carrying amount	407,336		407,336		$ 293,788
Hedged asset, total basis adjustments	(1,105)		(1,105)		(628)
Hedged asset, discontinued fair value, remaining adjustments	(1,105)		(1,105)		(628)
Closed portfolio, amortized cost	228,502		228,502		98,377
Closed portfolio, designated UPB	7,658		7,658		5,187
Hedged liability, carrying amount	(61,705)		(61,705)		(73,790)
Hedged liability, total basis adjustments	4,701		4,701		4,713
Hedged liability, discontinued fair value, remaining adjustments	4,701		4,701		$ 4,713
Pay-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	1,349	2,510	1,617	5,809
Receive-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(1,040)	(1,903)	(478)	(5,269)
Basis
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(22)	5	6	(126)
Foreign currency
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(12)	(62)	(2)	(122)
Pay-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	95	43	74	141
Receive-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	(13)	(6)	(16)	(19)
Futures
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	1	0	2	(1)
Risk Management Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	165	524	704	311
Net contractual interest expense on interest-rate swaps	(193)	(63)	(499)	(102)
Mortgage commitment derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	591	517	675	2,933
Credit enhancement derivatives fair value gains (losses), net
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains, net	47	(32)	61	(83)
Interest rate risk on held-for-investment mortgage loan | Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) in hedged item	(544)	(285)	(511)	(867)
Discontinued hedge related basis adjustment amortization	14	9	34	14
Change in unrealized gain (loss) in derivatives designated as hedging instruments	560	269	478	833
Interest accruals on hedging instruments	36	7	89	(10)
Total effect of fair value hedges	66	0	90	(30)
Interest rate risk on debt | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) in hedged item	176	1,477	606	3,848
Discontinued hedge related basis adjustment amortization	(223)	(145)	(618)	(329)
Change in unrealized gain (loss) in derivatives designated as hedging instruments	(66)	(1,289)	(137)	(3,381)
Interest accruals on hedging instruments	(191)	(108)	(713)	(54)
Total effect of fair value hedges	$ (304)	$ (65)	$ (862)	$ 84