Investment Securities - Investment Available for Sale (Details) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 86,097	$ 94,871
Allowance for Credit Losses	(4)	(1)
Gross Unrealized Gains	153	1,387
Gross Unrealized Losses	(10,943)	(996)
Securities available for sale (amortized cost of $86.1 billion and $94.9 billion and allowance for credit losses of $4 million and $1 million as of September 30, 2022 and December 31, 2021, respectively)	75,303	95,261
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,124	9,419
Allowance for Credit Losses	0	0
Gross Unrealized Gains	1	23
Gross Unrealized Losses	(98)	0
Securities available for sale (amortized cost of $86.1 billion and $94.9 billion and allowance for credit losses of $4 million and $1 million as of September 30, 2022 and December 31, 2021, respectively)	5,027	9,442
RMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	71,245	72,593
Allowance for Credit Losses	0	0
Gross Unrealized Gains	37	958
Gross Unrealized Losses	(10,069)	(931)
Securities available for sale (amortized cost of $86.1 billion and $94.9 billion and allowance for credit losses of $4 million and $1 million as of September 30, 2022 and December 31, 2021, respectively)	61,213	72,620
RMBS, Non-agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	666	792
Allowance for Credit Losses	(4)	(1)
Gross Unrealized Gains	112	205
Gross Unrealized Losses	(5)	0
Securities available for sale (amortized cost of $86.1 billion and $94.9 billion and allowance for credit losses of $4 million and $1 million as of September 30, 2022 and December 31, 2021, respectively)	769	996
RMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	71,911	73,385
Allowance for Credit Losses	(4)	(1)
Gross Unrealized Gains	149	1,163
Gross Unrealized Losses	(10,074)	(931)
Securities available for sale (amortized cost of $86.1 billion and $94.9 billion and allowance for credit losses of $4 million and $1 million as of September 30, 2022 and December 31, 2021, respectively)	61,982	73,616
CMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,055	9,237
Allowance for Credit Losses	0	0
Gross Unrealized Gains	2	195
Gross Unrealized Losses	(761)	(63)
Securities available for sale (amortized cost of $86.1 billion and $94.9 billion and allowance for credit losses of $4 million and $1 million as of September 30, 2022 and December 31, 2021, respectively)	7,296	9,369
Other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,007	2,830
Allowance for Credit Losses	0	0
Gross Unrealized Gains	1	6
Gross Unrealized Losses	(10)	(2)
Securities available for sale (amortized cost of $86.1 billion and $94.9 billion and allowance for credit losses of $4 million and $1 million as of September 30, 2022 and December 31, 2021, respectively)	998	2,834
Asset-backed Securities
Debt Securities, Available-for-sale [Line Items]
Securities available for sale (amortized cost of $86.1 billion and $94.9 billion and allowance for credit losses of $4 million and $1 million as of September 30, 2022 and December 31, 2021, respectively)	$ 231	$ 2,000
US Treasury and Agency securities \| Available-for-sale securities \| Government Contracts Concentration Risk
Debt Securities, Available-for-sale [Line Items]
Percentage of portfolio	98.00%	96.00%

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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