Securities - Schedule of Amortized Cost and Fair Value of Securities Available for Sale (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Schedule of Investments [Line Items]
Amortized Cost	$ 3,416	$ 3,380
Gross Unrealized Gains	36	84
Gross Unrealized Losses	(26)	(1)
Debt securities available for sale	3,426	3,463
U.S. Treasury
Schedule of Investments [Line Items]
Amortized Cost	205	600
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1)	0
Debt securities available for sale	204	600
U.S. government agencies
Schedule of Investments [Line Items]
Amortized Cost	154	172
Gross Unrealized Gains	1	0
Gross Unrealized Losses	0	0
Debt securities available for sale	155	172
U.S. government-sponsored entities
Schedule of Investments [Line Items]
Amortized Cost	194	160
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(2)	0
Debt securities available for sale	192	161
Agency mortgage-backed securities
Schedule of Investments [Line Items]
Amortized Cost	1,342	959
Gross Unrealized Gains	19	35
Gross Unrealized Losses	(4)	0
Debt securities available for sale	1,357	994
Agency collateralized mortgage obligations
Schedule of Investments [Line Items]
Amortized Cost	1,192	1,094
Gross Unrealized Gains	11	31
Gross Unrealized Losses	(17)	(1)
Debt securities available for sale	1,186	1,124
Commercial mortgage-backed securities
Schedule of Investments [Line Items]
Amortized Cost	294	361
Gross Unrealized Gains	5	17
Gross Unrealized Losses	(2)	0
Debt securities available for sale	297	378
States of the U.S. and political subdivisions (municipals)
Schedule of Investments [Line Items]
Amortized Cost	33	32
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Debt securities available for sale	33	32
Other debt securities
Schedule of Investments [Line Items]
Amortized Cost	2	2
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Debt securities available for sale	$ 2	$ 2

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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-SubTopic 10
-Section 50
-Paragraph 2
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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 excluding accrued interest, before allowance for credit loss, 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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-Publisher FASB
-Name Accounting Standards Codification
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Amount excluding accrued interest, 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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