Derivative Instruments - Derivatives 1 - Notional and FV Position (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Asset Derivatives
Notional Amount	$ 286,196	$ 450,981
Estimated Fair Value	395	1,225
Netting adjustment	(331)	(905)
Liability Derivatives
Notional Amount	228,204	288,198
Estimated Fair Value	(518)	(1,495)
Netting adjustment	849	995
Table Footnote [Abstract]
Cash collateral posted for derivative instruments	556	658
Cash collateral received for derivative instruments	38	568
Fair Value Hedging \| Designated as Hedging Instrument
Asset Derivatives
Notional Amount	46,952	0
Estimated Fair Value	0	0
Liability Derivatives
Notional Amount	0	0
Estimated Fair Value	0	0
Pay-fixed Swap
Asset Derivatives
Notional Amount	72,778	88,361
Estimated Fair Value	0	0
Liability Derivatives
Notional Amount	2,353	11,461
Estimated Fair Value	(59)	(595)
Pay-fixed Swap \| Fair Value Hedging \| Designated as Hedging Instrument
Asset Derivatives
Notional Amount	1,695	0
Estimated Fair Value	0	0
Liability Derivatives
Notional Amount	0	0
Estimated Fair Value	0	0
Receive-fixed Swap
Asset Derivatives
Notional Amount	35,651	92,315
Estimated Fair Value	2	233
Liability Derivatives
Notional Amount	44,478	33,919
Estimated Fair Value	(694)	(123)
Receive-fixed Swap \| Fair Value Hedging \| Designated as Hedging Instrument
Asset Derivatives
Notional Amount	45,257	0
Estimated Fair Value	0	0
Liability Derivatives
Notional Amount	0	0
Estimated Fair Value	0	0
Basis Swap
Asset Derivatives
Notional Amount	250	250
Estimated Fair Value	166	192
Liability Derivatives
Notional Amount	0	0
Estimated Fair Value	0	0
Foreign Currency Swap
Asset Derivatives
Notional Amount	239	237
Estimated Fair Value	43	57
Liability Derivatives
Notional Amount	104	239
Estimated Fair Value	(31)	(58)
Pay-fixed Swaption
Asset Derivatives
Notional Amount	4,430	5,530
Estimated Fair Value	62	37
Liability Derivatives
Notional Amount	410	2,025
Estimated Fair Value	(18)	(118)
Receive-fixed Swaption
Asset Derivatives
Notional Amount	390	3,355
Estimated Fair Value	9	346
Liability Derivatives
Notional Amount	950	700
Estimated Fair Value	(28)	(16)
Futures
Asset Derivatives
Notional Amount	0	64,398
Estimated Fair Value	0	0
Liability Derivatives
Notional Amount	0	0
Estimated Fair Value	0	0
Risk Management Derivatives
Asset Derivatives
Notional Amount	113,738	254,446
Estimated Fair Value	282	865
Accrued interest receivable (payable)	83	97
Netting adjustment	(331)	(905)
Liability Derivatives
Notional Amount	48,295	48,344
Estimated Fair Value	(830)	(910)
Accrued interest receivable (payable)	(29)	(105)
Netting adjustment	849	995
Risk Management Derivatives \| Not Designated as Hedging Instrument, Economic Hedge
Asset Derivatives
Notional Amount	113,738	254,446
Total net risk management derivatives	365	962
Liability Derivatives
Notional Amount	48,295	48,344
Total net risk management derivatives	(859)	(1,015)
Total risk management derivatives portfolio
Asset Derivatives
Notional Amount	160,690	254,446
Total net risk management derivatives	34	57
Liability Derivatives
Notional Amount	48,295	48,344
Total net risk management derivatives	(10)	(20)
Mortgage commitments to purchase whole loans
Asset Derivatives
Notional Amount	18,500	35,292
Estimated Fair Value	43	145
Liability Derivatives
Notional Amount	1,609	51
Estimated Fair Value	(2)	0
Forward contracts to purchase mortgage-related securities
Asset Derivatives
Notional Amount	76,309	144,215
Estimated Fair Value	254	844
Liability Derivatives
Notional Amount	28,596	607
Estimated Fair Value	(25)	0
Forward contracts to sell mortgage-related securities
Asset Derivatives
Notional Amount	19,017	199
Estimated Fair Value	14	0
Liability Derivatives
Notional Amount	140,605	227,828
Estimated Fair Value	(449)	(1,426)
Mortgage commitment derivatives
Asset Derivatives
Notional Amount	113,826	179,706
Estimated Fair Value	311	989
Netting adjustment	0	0
Liability Derivatives
Notional Amount	170,810	228,486
Estimated Fair Value	(476)	(1,426)
Netting adjustment	0	0
Credit enhancement derivatives
Asset Derivatives
Notional Amount	11,680	16,829
Estimated Fair Value	50	179
Liability Derivatives
Notional Amount	9,099	11,368
Estimated Fair Value	$ (32)	$ (49)

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Fair value of derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position. Includes all derivative assets subject to and not subject to master netting arrangements.

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Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position. Includes all derivatives liability subject and not subject to master netting arrangements.

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Nominal or face amount used to calculate payments on the derivative asset.

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