Derivative Instruments - Schedule of Notional and Fair Value Position (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Derivative [Line Items]
Notional amount	$ 474,869.0	$ 388,121.0
Asset Derivatives
Netting Adjustment	(362.0)	(283.0)
Derivative assets	179.0	202.0
Liability Derivatives
Derivatives liabilities at fair value	(154.0)	(140.0)
Table Footnote
Cash collateral posted for derivative instruments	2,000.0	2,900.0
Cash collateral received for derivative instruments	(3.0)	(5.0)
Total risk management derivatives portfolio
Derivative [Line Items]
Notional amount	332,643.0	299,557.0
Asset Derivatives
Netting Adjustment	(362.0)	(283.0)
Derivative assets	39.0	45.0
Liability Derivatives
Netting adjustment	2,367.0	3,200.0
Derivatives liabilities at fair value	(1.0)	(23.0)
Total risk management derivatives portfolio | Risk management derivatives designated as hedging instruments:
Derivative [Line Items]
Notional amount	36,761.0	38,541.0
Asset Derivatives
Derivative assets, gross	0.0	0.0
Liability Derivatives
Derivative liabilities, gross	0.0	0.0
Total risk management derivatives portfolio | Risk management derivatives not designated as hedging instruments:
Derivative [Line Items]
Notional amount	295,882.0	261,016.0
Asset Derivatives
Derivative assets, gross	401.0	328.0
Liability Derivatives
Derivative liabilities, gross	(2,368.0)	(3,223.0)
Pay-fixed | Risk management derivatives designated as hedging instruments:
Derivative [Line Items]
Notional amount	26,704.0	9,954.0
Asset Derivatives
Derivative assets, gross	0.0	0.0
Liability Derivatives
Derivative liabilities, gross	0.0	0.0
Pay-fixed | Risk management derivatives not designated as hedging instruments:
Derivative [Line Items]
Notional amount	146,628.0	136,648.0
Asset Derivatives
Derivative assets, gross	0.0	0.0
Liability Derivatives
Derivative liabilities, gross	0.0	0.0
Receive-fixed | Risk management derivatives designated as hedging instruments:
Derivative [Line Items]
Notional amount	10,057.0	28,587.0
Asset Derivatives
Derivative assets, gross	0.0	0.0
Liability Derivatives
Derivative liabilities, gross	0.0	0.0
Receive-fixed | Risk management derivatives not designated as hedging instruments:
Derivative [Line Items]
Notional amount	135,686.0	115,288.0
Asset Derivatives
Derivative assets, gross	71.0	76.0
Liability Derivatives
Derivative liabilities, gross	(2,164.0)	(3,085.0)
Basis | Risk management derivatives not designated as hedging instruments:
Derivative [Line Items]
Notional amount	250.0	250.0
Asset Derivatives
Derivative assets, gross	26.0	44.0
Liability Derivatives
Derivative liabilities, gross	0.0	0.0
Foreign currency | Risk management derivatives not designated as hedging instruments:
Derivative [Line Items]
Notional amount	310.0	316.0
Asset Derivatives
Derivative assets, gross	0.0	0.0
Liability Derivatives
Derivative liabilities, gross	(81.0)	(66.0)
Pay-fixed swaption | Risk management derivatives not designated as hedging instruments:
Derivative [Line Items]
Notional amount	7,006.0	5,816.0
Asset Derivatives
Derivative assets, gross	280.0	195.0
Liability Derivatives
Derivative liabilities, gross	(31.0)	(12.0)
Receive-fixed swaption | Risk management derivatives not designated as hedging instruments:
Derivative [Line Items]
Notional amount	5,916.0	2,666.0
Asset Derivatives
Derivative assets, gross	24.0	13.0
Liability Derivatives
Derivative liabilities, gross	(92.0)	(60.0)
Futures | Risk management derivatives not designated as hedging instruments:
Derivative [Line Items]
Notional amount	86.0	32.0
Asset Derivatives
Derivative assets, gross	0.0	0.0
Liability Derivatives
Derivative liabilities, gross	0.0	0.0
Mortgage commitment derivatives
Derivative [Line Items]
Notional amount	113,451.0	60,940.0
Asset Derivatives
Netting Adjustment	0.0	0.0
Derivative assets	112.0	112.0
Liability Derivatives
Netting adjustment	0.0	0.0
Derivatives liabilities at fair value	(137.0)	(104.0)
Mortgage commitments to purchase whole loans
Derivative [Line Items]
Notional amount	2,634.0	2,734.0
Asset Derivatives
Derivative assets	1.0	14.0
Liability Derivatives
Derivatives liabilities at fair value	(9.0)	0.0
Forward contracts to purchase mortgage-related securities
Derivative [Line Items]
Notional amount	31,883.0	14,264.0
Asset Derivatives
Derivative assets	3.0	98.0
Liability Derivatives
Derivatives liabilities at fair value	(118.0)	(2.0)
Forward contracts to sell mortgage-related securities
Derivative [Line Items]
Notional amount	78,934.0	43,942.0
Asset Derivatives
Derivative assets	108.0	0.0
Liability Derivatives
Derivatives liabilities at fair value	(10.0)	(102.0)
Credit enhancement derivatives
Derivative [Line Items]
Notional amount	28,775.0	27,624.0
Asset Derivatives
Derivative assets	28.0	45.0
Liability Derivatives
Derivatives liabilities at fair value	$ (16.0)	$ (13.0)