Investment Securities - Schedule of Amortized Cost, Unrealized Gains/(Losses) and Fair Value (Details) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 9,823
Securities available for sale at fair value	9,242	$ 8,707
Securities pledged as collateral	6,500	6,500
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	701	712
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(51)	(7)
Fair Value	650	705
Government agency issued MBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,364	5,062
Gross Unrealized Gains	3	42
Gross Unrealized Losses	(321)	(49)
Securities available for sale at fair value	5,046	5,055
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	499	509
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(37)	(5)
Fair Value	462	504
Government agency issued CMO
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,881	2,296
Gross Unrealized Gains	1	8
Gross Unrealized Losses	(167)	(47)
Securities available for sale at fair value	2,715	2,257
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	202	203
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(14)	(2)
Fair Value	188	201
Other U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	997	861
Gross Unrealized Gains	0	4
Gross Unrealized Losses	(61)	(15)
Securities available for sale at fair value	936	850
States and municipalities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	581	535
Gross Unrealized Gains	2	11
Gross Unrealized Losses	(38)	(1)
Securities available for sale at fair value	545	545
Securities available-for-sale, excluding interest only strip
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,823	8,754
Gross Unrealized Gains	6	65
Gross Unrealized Losses	(587)	(112)
Securities available for sale at fair value	$ 9,242	$ 8,707

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 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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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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Amount of accumulated unrecognized gain on investment in debt security measured at amortized cost (held-to-maturity).

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Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions.

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