Investment Securities - Investment Available for Sale (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 92,973	$ 94,871
Allowance for Credit Losses	(1)	(1)
Gross Unrealized Gains	449	1,387
Gross Unrealized Losses	(4,345)	(996)
Securities available for sale	89,076	95,261
U.S. Treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,521	9,419
Allowance for Credit Losses	0	0
Gross Unrealized Gains	5	23
Gross Unrealized Losses	(29)	0
Securities available for sale	9,497	9,442
RMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	71,292	72,593
Allowance for Credit Losses	0	0
Gross Unrealized Gains	231	958
Gross Unrealized Losses	(3,999)	(931)
Securities available for sale	67,524	72,620
RMBS, Non-agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	728	792
Allowance for Credit Losses	(1)	(1)
Gross Unrealized Gains	175	205
Gross Unrealized Losses	(1)	0
Securities available for sale	901	996
RMBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	72,020	73,385
Allowance for Credit Losses	(1)	(1)
Gross Unrealized Gains	406	1,163
Gross Unrealized Losses	(4,000)	(931)
Securities available for sale	68,425	73,616
CMBS, Agency
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,634	9,237
Allowance for Credit Losses	0	0
Gross Unrealized Gains	35	195
Gross Unrealized Losses	(304)	(63)
Securities available for sale	8,365	9,369
Other securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,798	2,830
Allowance for Credit Losses	0	0
Gross Unrealized Gains	3	6
Gross Unrealized Losses	(12)	(2)
Securities available for sale	2,789	2,834
Asset-backed Securities
Debt Securities, Available-for-sale [Line Items]
Securities available for sale	$ 2,000	$ 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	96.00%	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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