Investment Securities - Components of Available-for-Sale Investment Securities Portfolio (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 27,287	$ 27,370
Unrealized Gains	7	164
Unrealized Losses	(1,303)	(313)
Carrying value	25,991	27,221
U.S. treasury securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	17,152	15,799
Unrealized Gains	6	121
Unrealized Losses	(519)	(70)
Carrying value	16,639	15,850
U.S. agency debentures
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	162	200
Unrealized Gains	0	0
Unrealized Losses	(11)	(4)
Carrying value	151	196
Foreign government debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	59	61
Unrealized Gains	0	0
Unrealized Losses	0	0
Carrying value	59	61
Residential mortgage-backed securities \| Agency-issued mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,471	8,786
Unrealized Gains	1	13
Unrealized Losses	(626)	(210)
Carrying value	6,846	8,589
Residential mortgage-backed securities \| Agency-issued collateralized mortgage obligations—fixed rate
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	911	988
Unrealized Gains	0	3
Unrealized Losses	(51)	(9)
Carrying value	860	982
Agency-issued commercial mortgage-backed securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,532	1,536
Unrealized Gains	0	27
Unrealized Losses	(96)	(20)
Carrying value	$ 1,436	$ 1,543

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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