Investment Securities - Schedule of Amortized Cost, Unrealized Gains/(Losses) and Fair Value (Details) - USD ($) $ in Millions	Jun. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 9,830
Securities available for sale at fair value	8,941	$ 8,707
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	687	712
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(86)	(7)
Fair Value	601	705
Government agency issued MBS
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,268	5,062
Gross Unrealized Gains	2	42
Gross Unrealized Losses	(491)	(49)
Securities available for sale at fair value	4,779	5,055
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	486	509
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(62)	(5)
Fair Value	424	504
Government agency issued CMO
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,867	2,296
Gross Unrealized Gains	0	8
Gross Unrealized Losses	(241)	(47)
Securities available for sale at fair value	2,626	2,257
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	201	203
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(24)	(2)
Fair Value	177	201
Other U.S. government agencies
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	1,071	861
Gross Unrealized Gains	1	4
Gross Unrealized Losses	(98)	(15)
Securities available for sale at fair value	974	850
States and municipalities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	623	535
Gross Unrealized Gains	0	11
Gross Unrealized Losses	(61)	(1)
Securities available for sale at fair value	562	545
Securities available-for-sale, excluding interest only strip
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,829	8,754
Gross Unrealized Gains	3	65
Gross Unrealized Losses	(891)	(112)
Securities available for sale at fair value	8,941	8,707
Securities available-for-sale, excluding interest only strip \| Collateral Pledged
Debt Securities, Available-for-sale [Line Items]
Securities available for sale at fair value	$ 6,500	$ 6,500

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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