Derivative Instruments - Notional and Fair Value Position (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Derivative [Line Items]
Notional Amount	$ 439,597	$ 474,869
Asset Derivatives
Derivative assets, gross amount offset	(399)	(362)
Derivative assets	127	179
Liability Derivatives
Derivatives liabilities at fair value	(157)	(154)
Table Footnote [Abstract]
Cash collateral posted for derivative instruments	1,600	2,000
Cash collateral received for derivative instruments	(76)	(3)
Total risk management derivatives designated as hedging instruments
Derivative [Line Items]
Notional Amount	327,028	332,643
Asset Derivatives
Derivative assets, gross amount offset	(399)	(362)
Derivative assets	51	39
Liability Derivatives
Netting adjustment	1,893	2,367
Derivatives liabilities at fair value	(27)	(1)
Total risk management derivatives designated as hedging instruments | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	30,429	36,761
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Total risk management derivatives designated as hedging instruments | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	296,599	295,882
Asset Derivatives
Derivative assets, gross	450	401
Liability Derivatives
Derivative liabilities, gross	(1,920)	(2,368)
Pay-fixed | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	21,028	26,704
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Pay-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	161,278	146,628
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Receive-fixed | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	9,401	10,057
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Receive-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	121,759	135,686
Asset Derivatives
Derivative assets, gross	142	71
Liability Derivatives
Derivative liabilities, gross	(1,739)	(2,164)
Basis | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	250	250
Asset Derivatives
Derivative assets, gross	30	26
Liability Derivatives
Derivative liabilities, gross	0	0
Foreign currency | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	320	310
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	(70)	(81)
Pay-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	7,006	7,006
Asset Derivatives
Derivative assets, gross	254	280
Liability Derivatives
Derivative liabilities, gross	(19)	(31)
Receive-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	5,916	5,916
Asset Derivatives
Derivative assets, gross	24	24
Liability Derivatives
Derivative liabilities, gross	(92)	(92)
Futures | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	70	86
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Mortgage commitment derivatives
Derivative [Line Items]
Notional Amount	82,988	113,451
Asset Derivatives
Derivative assets, gross amount offset	0	0
Derivative assets	52	112
Liability Derivatives
Netting adjustment	0	0
Derivatives liabilities at fair value	(111)	(137)
Mortgage commitments to purchase whole loans
Derivative [Line Items]
Notional Amount	3,384	2,634
Asset Derivatives
Derivative assets	7	1
Liability Derivatives
Derivatives liabilities at fair value	(1)	(9)
Forward contracts to purchase mortgage-related securities
Derivative [Line Items]
Notional Amount	24,321	31,883
Asset Derivatives
Derivative assets	43	3
Liability Derivatives
Derivatives liabilities at fair value	(5)	(118)
Forward contracts to sell mortgage-related securities
Derivative [Line Items]
Notional Amount	55,283	78,934
Asset Derivatives
Derivative assets	2	108
Liability Derivatives
Derivatives liabilities at fair value	(105)	(10)
Credit enhancement derivatives
Derivative [Line Items]
Notional Amount	29,581	28,775
Asset Derivatives
Derivative assets	24	28
Liability Derivatives
Derivatives liabilities at fair value	$ (19)	$ (16)