Investment Securities - Major Components of AFS Investment Securities Portfolio (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Investment Holdings [Line Items]
Total AFS securities	$ 27,370	$ 30,245
Unrealized Gains	164	683
Unrealized Losses	(313)	(15)
Available-for-sale securities	27,221	30,913
U.S. treasury securities
Investment Holdings [Line Items]
Total AFS securities	15,799	4,198
Unrealized Gains	121	272
Unrealized Losses	(70)	0
Available-for-sale securities	15,850	4,470
U.S. agency debentures
Investment Holdings [Line Items]
Total AFS securities	200	234
Unrealized Gains	0	4
Unrealized Losses	(4)	(1)
Available-for-sale securities	196	237
Foreign government debt securities
Investment Holdings [Line Items]
Total AFS securities	61	24
Unrealized Gains	0	0
Unrealized Losses	0	0
Available-for-sale securities	61	24
Residential mortgage-backed securities \| Agency-issued mortgage-backed securities
Investment Holdings [Line Items]
Total AFS securities	8,786	13,271
Unrealized Gains	13	233
Unrealized Losses	(210)	(1)
Available-for-sale securities	8,589	13,503
Residential mortgage-backed securities \| Agency-issued collateralized mortgage obligations - fixed rate
Investment Holdings [Line Items]
Total AFS securities	988	8,077
Unrealized Gains	3	40
Unrealized Losses	(9)	(10)
Available-for-sale securities	982	8,107
Agency-issued commercial mortgage-backed securities
Investment Holdings [Line Items]
Total AFS securities	1,536	4,441
Unrealized Gains	27	134
Unrealized Losses	(20)	(3)
Available-for-sale securities	$ 1,543	$ 4,572

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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Amount, before tax, of unrealized loss 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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Amortized cost of 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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