Derivative Instruments - Notional and Fair Value Position (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Derivative [Line Items]
Notional Amount	$ 414,792	$ 388,121
Asset Derivatives
Derivative assets, gross amount offset	(333)	(283)
Derivative assets	102	202
Liability Derivatives
Derivatives liabilities at fair value	(78)	(140)
Table Footnote [Abstract]
Cash collateral posted for derivative instruments	2,900	2,900
Cash collateral received for derivative instruments	(4)	(5)
Total risk management derivatives designated as hedging instruments
Derivative [Line Items]
Notional Amount	325,009	299,557
Asset Derivatives
Derivative assets, gross amount offset	(333)	(283)
Derivative assets	18	45
Liability Derivatives
Netting adjustment	3,266	3,200
Derivatives liabilities at fair value	(14)	(23)
Total risk management derivatives designated as hedging instruments | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	34,588	38,541
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	290,421	261,016
Asset Derivatives
Derivative assets, gross	351	328
Liability Derivatives
Derivative liabilities, gross	(3,280)	(3,223)
Pay-fixed | Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	9,836	9,954
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	148,866	136,648
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	24,752	28,587
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	132,426	115,288
Asset Derivatives
Derivative assets, gross	69	76
Liability Derivatives
Derivative liabilities, gross	(3,120)	(3,085)
Basis | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	250	250
Asset Derivatives
Derivative assets, gross	41	44
Liability Derivatives
Derivative liabilities, gross	0	0
Foreign currency | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	313	316
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	(72)	(66)
Pay-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	5,816	5,816
Asset Derivatives
Derivative assets, gross	223	195
Liability Derivatives
Derivative liabilities, gross	(18)	(12)
Receive-fixed | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	2,666	2,666
Asset Derivatives
Derivative assets, gross	18	13
Liability Derivatives
Derivative liabilities, gross	(70)	(60)
Futures | Not Designated as Hedging Instrument
Derivative [Line Items]
Notional Amount	84	32
Asset Derivatives
Derivative assets, gross	0	0
Liability Derivatives
Derivative liabilities, gross	0	0
Mortgage commitment derivatives
Derivative [Line Items]
Notional Amount	61,097	60,940
Asset Derivatives
Derivative assets, gross amount offset	0	0
Derivative assets	43	112
Liability Derivatives
Netting adjustment	0	0
Derivatives liabilities at fair value	(51)	(104)
Mortgage commitments to purchase whole loans
Derivative [Line Items]
Notional Amount	3,305	2,734
Asset Derivatives
Derivative assets	6	14
Liability Derivatives
Derivatives liabilities at fair value	(1)	0
Forward contracts to purchase mortgage-related securities
Derivative [Line Items]
Notional Amount	17,361	14,264
Asset Derivatives
Derivative assets	31	98
Liability Derivatives
Derivatives liabilities at fair value	(11)	(2)
Forward contracts to sell mortgage-related securities
Derivative [Line Items]
Notional Amount	40,431	43,942
Asset Derivatives
Derivative assets	6	0
Liability Derivatives
Derivatives liabilities at fair value	(39)	(102)
Credit enhancement derivatives
Derivative [Line Items]
Notional Amount	28,686	27,624
Asset Derivatives
Derivative assets	41	45
Liability Derivatives
Derivatives liabilities at fair value	$ (13)	$ (13)