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Investment Securities - Investment Available for Sale (Details) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 92,995	$ 88,063
Allowance for Credit Losses	(4)	(4)
Gross Unrealized Gains	148	214
Gross Unrealized Losses	(10,126)	(9,156)
Fair Value	83,013	79,117
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	6,114	5,330
Allowance for Credit Losses	0	0
Gross Unrealized Gains	5	1
Gross Unrealized Losses	(9)	(49)
Fair Value	6,110	5,282
RMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	74,177	71,294
Allowance for Credit Losses	0	0
Gross Unrealized Gains	57	104
Gross Unrealized Losses	(9,527)	(8,450)
Fair Value	64,707	62,948
RMBS, Non-agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	567	610
Allowance for Credit Losses	(4)	(4)
Gross Unrealized Gains	64	89
Gross Unrealized Losses	(6)	(5)
Fair Value	621	690
Total RMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	74,744	71,904
Allowance for Credit Losses	(4)	(4)
Gross Unrealized Gains	121	193
Gross Unrealized Losses	(9,533)	(8,455)
Fair Value	65,328	63,638
Agency CMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,389	8,961
Allowance for Credit Losses	0	0
Gross Unrealized Gains	17	14
Gross Unrealized Losses	(581)	(652)
Fair Value	7,825	8,323
Other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,748	1,868
Allowance for Credit Losses	0	0
Gross Unrealized Gains	5	6
Gross Unrealized Losses	(3)	0
Fair Value	3,750	1,874
Asset-backed Securities
Debt Securities, Available-for-sale [Line Items]
Fair Value	$ 2,000	$ 1,400

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