Derivative Instruments - Notional and Fair Value Position (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Derivative [Line Items]
Notional amount	$ 409,375	$ 366,384
Asset Derivatives
Derivative assets, gross amount offset	(163)	(237)
Derivative assets	498	171
Liability Derivatives
Derivatives liabilities at fair value	(923)	(233)
Table Footnote [Abstract]
Cash collateral posted for derivative instruments	4,700	966
Cash collateral received for derivative instruments	8	30
Total risk management derivatives portfolio
Derivative [Line Items]
Notional amount	274,397	164,742
Asset Derivatives
Derivative assets, gross amount offset	(163)	(237)
Derivative assets	76	2
Liability Derivatives
Netting adjustment	4,833	1,173
Derivatives liabilities at fair value	(44)	(15)
Total risk management derivatives portfolio | Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	42,147	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	232,250	119,709
Asset Derivatives
Derivative assets, gross	239	239
Liability Derivatives
Derivative liabilities, gross	(4,877)	(1,188)
Pay-fixed Swap | Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	6,221	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	89,832	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	35,926	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	93,469	56,874
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	(4,683)	(1,131)
Basis Swap | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	41,250	250
Asset Derivatives
Derivative assets, gross	31	152
Liability Derivatives
Derivative liabilities, gross	0	0
Foreign Currency Swap | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	277	336
Asset Derivatives
Derivative assets, gross	0	25
Liability Derivatives
Derivative liabilities, gross	(130)	(34)
Pay-fixed Swaption | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	5,286	4,341
Asset Derivatives
Derivative assets, gross	203	52
Liability Derivatives
Derivative liabilities, gross	(20)	(2)
Receive-fixed Swaption | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional amount	2,136	1,091
Asset Derivatives
Derivative assets, gross	5	10
Liability Derivatives
Derivative liabilities, gross	(44)	(21)
Mortgage commitment derivatives
Derivative [Line Items]
Notional amount	110,522	182,386
Asset Derivatives
Derivative assets, gross amount offset	0	0
Derivative assets	420	169
Liability Derivatives
Netting adjustment	0	0
Derivatives liabilities at fair value	(814)	(197)
Mortgage commitments to purchase whole loans
Derivative [Line Items]
Notional amount	5,774	13,192
Asset Derivatives
Derivative assets	4	17
Liability Derivatives
Derivatives liabilities at fair value	(78)	(5)
Forward contracts to purchase mortgage-related securities
Derivative [Line Items]
Notional amount	43,304	58,021
Asset Derivatives
Derivative assets	5	83
Liability Derivatives
Derivatives liabilities at fair value	(732)	(34)
Forward contracts to sell mortgage-related securities
Derivative [Line Items]
Notional amount	61,444	111,173
Asset Derivatives
Derivative assets	411	69
Liability Derivatives
Derivatives liabilities at fair value	(4)	(158)
Other
Derivative [Line Items]
Notional amount	24,456	19,256
Asset Derivatives
Derivative assets	2	0
Liability Derivatives
Derivatives liabilities at fair value	$ (65)	$ (21)