Derivative Instruments - Notional and Fair Value Position (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Derivative [Line Items]
Notional amount	$ 398,086	$ 366,384
Asset Derivatives
Derivative assets, gross amount offset	63	(237)
Derivative assets	892	171
Liability Derivatives
Netting adjustment	3,540
Derivatives liabilities at fair value	(622)	(233)
Table Footnote [Abstract]
Cash collateral posted for derivative instruments	3,700	966
Cash collateral received for derivative instruments	83	30
Total risk management derivatives portfolio
Derivative [Line Items]
Notional amount	250,026	164,742
Asset Derivatives
Derivative assets, gross amount offset	63	(237)
Derivative assets	258	2
Liability Derivatives
Netting adjustment	3,540	1,173
Derivatives liabilities at fair value	(79)	(15)
Total risk management derivatives portfolio | Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	51,863	45,033
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Total risk management derivatives portfolio | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	198,163	119,709
Asset Derivatives
Derivative assets, gross	195	239
Liability Derivatives
Derivative liabilities, gross	(3,619)	(1,188)
Pay-fixed Swap | Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	5,920	4,347
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Pay-fixed Swap | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	74,548	56,817
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Receive-fixed Swap | Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	45,943	40,686
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Receive-fixed Swap | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	75,951	56,874
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	(3,514)	(1,131)
Basis Swap | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	41,250	250
Asset Derivatives
Derivative assets, gross	35	152
Liability Derivatives
Derivative liabilities, gross	0	0
Foreign Currency Swap | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	302	336
Asset Derivatives
Derivative assets, gross	0	25
Liability Derivatives
Derivative liabilities, gross	(69)	(34)
Pay-fixed Swaption | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	4,631	4,341
Asset Derivatives
Derivative assets, gross	151	52
Liability Derivatives
Derivative liabilities, gross	(3)	(2)
Receive-fixed Swaption | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	1,481	1,091
Asset Derivatives
Derivative assets, gross	9	10
Liability Derivatives
Derivative liabilities, gross	(33)	(21)
Mortgage commitment derivatives
Derivative [Line Items]
Notional amount	123,961	182,386
Asset Derivatives
Derivative assets, gross amount offset	0	0
Derivative assets	631	169
Liability Derivatives
Netting adjustment	0	0
Derivatives liabilities at fair value	(498)	(197)
Mortgage commitments to purchase whole loans
Derivative [Line Items]
Notional amount	7,096	13,192
Asset Derivatives
Derivative assets	36	17
Liability Derivatives
Derivatives liabilities at fair value	(12)	(5)
Forward contracts to purchase mortgage-related securities
Derivative [Line Items]
Notional amount	44,811	58,021
Asset Derivatives
Derivative assets	358	83
Liability Derivatives
Derivatives liabilities at fair value	(93)	(34)
Forward contracts to sell mortgage-related securities
Derivative [Line Items]
Notional amount	72,054	111,173
Asset Derivatives
Derivative assets	237	69
Liability Derivatives
Derivatives liabilities at fair value	(393)	(158)
Other
Derivative [Line Items]
Notional amount	24,099	19,256
Asset Derivatives
Derivative assets	3	0
Liability Derivatives
Derivatives liabilities at fair value	$ (45)	$ (21)