Derivative Instruments - Notional and Fair Value Position (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Derivative [Line Items]
Notional Amount	$ 545,366	$ 474,869
Asset Derivatives
Derivative assets, gross amount offset	(277)	(362)
Derivative assets	144	179
Liability Derivatives
Derivatives liabilities at fair value	(179)	(154)
Table Footnote [Abstract]
Cash collateral posted for derivative instruments	1,100	2,000
Cash collateral received for derivative instruments	(79)	(3)
Total risk management derivatives designated as hedging instruments
Derivative [Line Items]
Notional Amount	386,021	332,643
Asset Derivatives
Derivative assets, gross amount offset	(277)	(362)
Derivative assets	51	39
Liability Derivatives
Netting adjustment	1,324	2,367
Derivatives liabilities at fair value	(14)	(1)
Total risk management derivatives designated as hedging instruments | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	49,585	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	336,436	295,882
Asset Derivatives
Derivative assets, gross	328	401
Liability Derivatives
Derivative liabilities, gross	(1,338)	(2,368)
Pay-fixed | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	31,906	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	166,988	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	17,679	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	147,638	135,686
Asset Derivatives
Derivative assets, gross	118	71
Liability Derivatives
Derivative liabilities, gross	(1,190)	(2,164)
Basis | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	250	250
Asset Derivatives
Derivative assets, gross	27	26
Liability Derivatives
Derivative liabilities, gross	0	0
Foreign currency | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	334	310
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	(56)	(81)
Pay-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	7,986	7,006
Asset Derivatives
Derivative assets, gross	175	280
Liability Derivatives
Derivative liabilities, gross	0	(31)
Receive-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	7,691	5,916
Asset Derivatives
Derivative assets, gross	8	24
Liability Derivatives
Derivative liabilities, gross	(92)	(92)
Futures | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	5,549	86
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Mortgage commitment derivatives
Derivative [Line Items]
Notional Amount	129,798	113,451
Asset Derivatives
Derivative assets, gross amount offset	0	0
Derivative assets	62	112
Liability Derivatives
Netting adjustment	0	0
Derivatives liabilities at fair value	(156)	(137)
Mortgage commitments to purchase whole loans
Derivative [Line Items]
Notional Amount	4,666	2,634
Asset Derivatives
Derivative assets	5	1
Liability Derivatives
Derivatives liabilities at fair value	(5)	(9)
Forward contracts to purchase mortgage-related securities
Derivative [Line Items]
Notional Amount	41,157	31,883
Asset Derivatives
Derivative assets	46	3
Liability Derivatives
Derivatives liabilities at fair value	(28)	(118)
Forward contracts to sell mortgage-related securities
Derivative [Line Items]
Notional Amount	83,975	78,934
Asset Derivatives
Derivative assets	11	108
Liability Derivatives
Derivatives liabilities at fair value	(123)	(10)
Credit enhancement derivatives
Derivative [Line Items]
Notional Amount	29,547	28,775
Asset Derivatives
Derivative assets	31	28
Liability Derivatives
Derivatives liabilities at fair value	$ (9)	$ (16)