Derivative Instruments - FV Gains and Losses (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	$ 558	$ (2,832)	$ (2,110)
Net accrual of periodic settlements	29,587	24,866	21,293
Pay-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	2,207	(2,764)	(3,964)
Receive-fixed
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(1,783)	2,226	3,685
Basis
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(51)	43	46
Foreign currency
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(26)	23	24
Pay-fixed swaption
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	38	(146)	(380)
Receive-fixed swaption
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	(217)	595	117
Futures
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	1	(76)	273
Risk management derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	185	(360)	(1,032)
Net accrual of periodic settlements	16	(261)	(833)
Mortgage commitment derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	551	(2,654)	(1,043)
Credit enhancement derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Derivative fair value gains (losses), net	$ (178)	$ 182	$ (35)