Derivative Instruments - Derivatives 2 - FV Gains and Losses (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	$ (507)	$ (569)	$ 641	$ (1,934)
Net contractual interest income (expense) on interest-rate swaps	8,286	5,777	15,028	11,124
Interest income on mortgage loans	24,932	27,007	48,285	55,945
Long-term debt	(16,820)	(21,460)	(33,637)	(45,437)
Hedged Asset, Fair Value Hedge	125,321		125,321
Hedged Liability, Fair Value Hedge	(62,688)		(62,688)
Hedged Asset, Fair Value Hedge, Cumulative Increase (Decrease)	70		70
Hedged Liability, Fair Value Hedge, Cumulative Increase (Decrease)	771		771
Hedged Asset, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)	70		70
Hedged Liability, Discontinued Fair Value Hedge, Cumulative Increase (Decrease)	771		771
Hedged Asset, Fair Value Hedge, Last-of-Layer, Cumulative Increase (Decrease)	40,570		40,570
Hedged Asset, Fair Value Hedge, Last-of-Layer, Amount	1,728		1,728
Pay-fixed Swap
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	(695)	(94)	1,512	(4,123)
Receive-fixed Swap
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	757	191	(1,098)	3,534
Basis Swap
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	19	17	(27)	73
Foreign Currency Swap
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	4	4	(4)	(34)
Pay-fixed Swaption
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	(58)	(13)	49	(161)
Receive-fixed Swaption
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	30	25	(209)	657
Futures
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	0	(4)	1	(75)
Risk Management Derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	64	62	220	(299)
Net contractual interest income (expense) on interest-rate swaps	7	(64)	(4)	(170)
Mortgage commitment derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	(553)	(662)	529	(1,655)
Credit enhancement derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Total derivatives fair value gains (losses), net	(18)	$ 31	(108)	$ 20
Interest rate risk on held-for-investment mortgage loan | Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) in hedged item	106		70
Change in unrealized gain (loss) in derivatives designated as hedging instruments	(106)		(70)
Interest accruals on hedging instruments	(5)		(5)
Total effect of fair value hedges	(5)		(5)
Interest rate risk on debt | Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) in hedged item	(390)		805
Change in unrealized gain (loss) in derivatives designated as hedging instruments	423		(791)
Interest accruals on hedging instruments	59		113
Discontinued hedge related basis adjustment amortization	(21)		(34)
Total effect of fair value hedges	$ 71		$ 93