Derivative Instruments - Notional and Fair Value Position (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Derivative [Line Items]
Notional Amount	$ 517,799	$ 474,869
Asset Derivatives
Derivative assets, gross amount offset	(403)	(362)
Derivative assets	205	179
Liability Derivatives
Derivatives liabilities at fair value	(293)	(154)
Table Footnote [Abstract]
Cash collateral posted for derivative instruments	1,300	2,000
Cash collateral received for derivative instruments	(208)	(3)
Total risk management derivatives designated as hedging instruments
Derivative [Line Items]
Notional Amount	388,050	332,643
Asset Derivatives
Derivative assets, gross amount offset	(403)	(362)
Derivative assets	42	39
Liability Derivatives
Netting adjustment	1,480	2,367
Derivatives liabilities at fair value	(87)	(1)
Total risk management derivatives designated as hedging instruments | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	46,833	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	341,217	295,882
Asset Derivatives
Derivative assets, gross	445	401
Liability Derivatives
Derivative liabilities, gross	(1,567)	(2,368)
Pay-fixed | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	29,648	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	188,357	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	17,185	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	136,451	135,686
Asset Derivatives
Derivative assets, gross	120	71
Liability Derivatives
Derivative liabilities, gross	(1,436)	(2,164)
Basis | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	250	250
Asset Derivatives
Derivative assets, gross	24	26
Liability Derivatives
Derivative liabilities, gross	0	0
Foreign currency | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	341	310
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	(49)	(81)
Pay-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	7,546	7,006
Asset Derivatives
Derivative assets, gross	282	280
Liability Derivatives
Derivative liabilities, gross	(17)	(31)
Receive-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	6,916	5,916
Asset Derivatives
Derivative assets, gross	19	24
Liability Derivatives
Derivative liabilities, gross	(65)	(92)
Futures | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	1,356	86
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Mortgage commitment derivatives
Derivative [Line Items]
Notional Amount	99,818	113,451
Asset Derivatives
Derivative assets, gross amount offset	0	0
Derivative assets	141	112
Liability Derivatives
Netting adjustment	0	0
Derivatives liabilities at fair value	(192)	(137)
Mortgage commitments to purchase whole loans
Derivative [Line Items]
Notional Amount	4,600	2,634
Asset Derivatives
Derivative assets	19	1
Liability Derivatives
Derivatives liabilities at fair value	0	(9)
Forward contracts to purchase mortgage-related securities
Derivative [Line Items]
Notional Amount	30,345	31,883
Asset Derivatives
Derivative assets	122	3
Liability Derivatives
Derivatives liabilities at fair value	0	(118)
Forward contracts to sell mortgage-related securities
Derivative [Line Items]
Notional Amount	64,873	78,934
Asset Derivatives
Derivative assets	0	108
Liability Derivatives
Derivatives liabilities at fair value	(192)	(10)
Credit enhancement derivatives
Derivative [Line Items]
Notional Amount	29,931	28,775
Asset Derivatives
Derivative assets	22	28
Liability Derivatives
Derivatives liabilities at fair value	$ (14)	$ (16)