Investment Securities - Investment Available for Sale (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 88,063	$ 87,047
Allowance for Credit Losses	(4)	(3)
Gross Unrealized Gains	214	154
Gross Unrealized Losses	(9,156)	(10,279)
Fair Value	79,117	76,919
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,330	5,129
Allowance for Credit Losses	0	0
Gross Unrealized Gains	1	2
Gross Unrealized Losses	(49)	(90)
Fair Value	5,282	5,041
RMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	71,294	71,212
Allowance for Credit Losses	0	0
Gross Unrealized Gains	104	53
Gross Unrealized Losses	(8,450)	(9,413)
Fair Value	62,948	61,852
RMBS, Non-agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	610	653
Allowance for Credit Losses	(4)	(3)
Gross Unrealized Gains	89	93
Gross Unrealized Losses	(5)	(6)
Fair Value	690	737
Total RMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	71,904	71,865
Allowance for Credit Losses	(4)	(3)
Gross Unrealized Gains	193	146
Gross Unrealized Losses	(8,455)	(9,419)
Fair Value	63,638	62,589
Agency CMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,961	8,626
Allowance for Credit Losses	0	0
Gross Unrealized Gains	14	4
Gross Unrealized Losses	(652)	(760)
Fair Value	8,323	7,870
Other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,868	1,427
Allowance for Credit Losses	0	0
Gross Unrealized Gains	6	2
Gross Unrealized Losses	0	(10)
Fair Value	1,874	1,419
Asset-backed Securities
Debt Securities, Available-for-sale [Line Items]
Fair Value	$ 1,400	$ 707

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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