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Investment Securities - Investment Available for Sale (Details) - USD ($) $ in Millions	Jun. 30, 2025	Dec. 31, 2024
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 95,424	$ 92,995
Allowance for Credit Losses	(3)	(4)
Gross Unrealized Gains	241	148
Gross Unrealized Losses	(8,466)	(10,126)
Fair Value	87,196	83,013
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,397	6,114
Allowance for Credit Losses	0	0
Gross Unrealized Gains	20	5
Gross Unrealized Losses	(8)	(9)
Fair Value	8,409	6,110
RMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	74,225	74,177
Allowance for Credit Losses	0	0
Gross Unrealized Gains	117	57
Gross Unrealized Losses	(8,018)	(9,527)
Fair Value	66,324	64,707
RMBS, Non-agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	547	567
Allowance for Credit Losses	(3)	(4)
Gross Unrealized Gains	71	64
Gross Unrealized Losses	(2)	(6)
Fair Value	613	621
Total RMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	74,772	74,744
Allowance for Credit Losses	(3)	(4)
Gross Unrealized Gains	188	121
Gross Unrealized Losses	(8,020)	(9,533)
Fair Value	66,937	65,328
Agency CMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,848	8,389
Allowance for Credit Losses	0	0
Gross Unrealized Gains	29	17
Gross Unrealized Losses	(437)	(581)
Fair Value	8,440	7,825
Other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	3,407	3,748
Allowance for Credit Losses	0	0
Gross Unrealized Gains	4	5
Gross Unrealized Losses	(1)	(3)
Fair Value	3,410	3,750
Asset-backed Securities
Debt Securities, Available-for-sale [Line Items]
Fair Value	$ 1,500	$ 2,000

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