Investment Securities - Investment Available for Sale (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 90,785	$ 87,047
Allowance for Credit Losses	(2)	(3)
Gross Unrealized Gains	224	154
Gross Unrealized Losses	(9,082)	(10,279)
Securities available for sale (amortized cost of $90.8 billion and $87.0 billion and allowance for credit losses of $2 million and $3 million as of March 31, 2023 and December 31, 2022, respectively)	81,925	76,919
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,230	5,129
Allowance for Credit Losses	0	0
Gross Unrealized Gains	3	2
Gross Unrealized Losses	(70)	(90)
Securities available for sale (amortized cost of $90.8 billion and $87.0 billion and allowance for credit losses of $2 million and $3 million as of March 31, 2023 and December 31, 2022, respectively)	5,163	5,041
RMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	73,853	71,212
Allowance for Credit Losses	0	0
Gross Unrealized Gains	106	53
Gross Unrealized Losses	(8,338)	(9,413)
Securities available for sale (amortized cost of $90.8 billion and $87.0 billion and allowance for credit losses of $2 million and $3 million as of March 31, 2023 and December 31, 2022, respectively)	65,621	61,852
RMBS, Non-agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	641	653
Allowance for Credit Losses	(2)	(3)
Gross Unrealized Gains	97	93
Gross Unrealized Losses	(6)	(6)
Securities available for sale (amortized cost of $90.8 billion and $87.0 billion and allowance for credit losses of $2 million and $3 million as of March 31, 2023 and December 31, 2022, respectively)	730	737
RMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	74,494	71,865
Allowance for Credit Losses	(2)	(3)
Gross Unrealized Gains	203	146
Gross Unrealized Losses	(8,344)	(9,419)
Securities available for sale (amortized cost of $90.8 billion and $87.0 billion and allowance for credit losses of $2 million and $3 million as of March 31, 2023 and December 31, 2022, respectively)	66,351	62,589
CMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,076	8,626
Allowance for Credit Losses	0	0
Gross Unrealized Gains	14	4
Gross Unrealized Losses	(661)	(760)
Securities available for sale (amortized cost of $90.8 billion and $87.0 billion and allowance for credit losses of $2 million and $3 million as of March 31, 2023 and December 31, 2022, respectively)	8,429	7,870
Other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,985	1,427
Allowance for Credit Losses	0	0
Gross Unrealized Gains	4	2
Gross Unrealized Losses	(7)	(10)
Securities available for sale (amortized cost of $90.8 billion and $87.0 billion and allowance for credit losses of $2 million and $3 million as of March 31, 2023 and December 31, 2022, respectively)	1,982	1,419
Asset-backed Securities
Debt Securities, Available-for-sale [Line Items]
Securities available for sale (amortized cost of $90.8 billion and $87.0 billion and allowance for credit losses of $2 million and $3 million as of March 31, 2023 and December 31, 2022, respectively)	$ 1,300	$ 707
US Treasury and Agency securities \| Available-for-sale securities \| Government Contracts Concentration Risk
Debt Securities, Available-for-sale [Line Items]
Percentage of portfolio	97.00%	97.00%

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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