Investment Securities - Summary of Investment Securities (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Available-for-sale securities
Amortized Cost	$ 2,084,000,000	$ 1,788,000,000
Gross Unrealized Gains	1,000,000	20,000,000
Gross Unrealized Losses	(75,000,000)	(4,000,000)
Fair Value	2,010,000,000	1,804,000,000
Held-to-maturity securities
Amortized Cost	190,000,000	205,000,000
Gross Unrealized Gains	0	4,000,000
Gross Unrealized Losses	(4,000,000)	0
Fair Value	186,000,000	209,000,000
Securities of a single issuer that exceeded 10% of stockholders' equity	0	0
Agency - Commercial
Available-for-sale securities
Amortized Cost	1,086,000,000	739,000,000
Gross Unrealized Gains	0	8,000,000
Gross Unrealized Losses	(28,000,000)	0
Fair Value	1,058,000,000	747,000,000
Held-to-maturity securities
Amortized Cost	93,000,000	99,000,000
Gross Unrealized Gains	0	1,000,000
Gross Unrealized Losses	(2,000,000)	0
Fair Value	91,000,000	100,000,000
Agency - Residential
Available-for-sale securities
Amortized Cost	649,000,000	690,000,000
Gross Unrealized Gains	0	9,000,000
Gross Unrealized Losses	(34,000,000)	(3,000,000)
Fair Value	615,000,000	696,000,000
Held-to-maturity securities
Amortized Cost	97,000,000	106,000,000
Gross Unrealized Gains	0	3,000,000
Gross Unrealized Losses	(2,000,000)	0
Fair Value	95,000,000	109,000,000
Corporate debt obligations
Available-for-sale securities
Amortized Cost	71,000,000	70,000,000
Gross Unrealized Gains	1,000,000	3,000,000
Gross Unrealized Losses	0	0
Fair Value	72,000,000	73,000,000
Municipal obligations
Available-for-sale securities
Amortized Cost	19,000,000	20,000,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	19,000,000	20,000,000
Other MBS
Available-for-sale securities
Amortized Cost	258,000,000	268,000,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(13,000,000)	(1,000,000)
Fair Value	245,000,000	267,000,000
Certificate of deposits
Available-for-sale securities
Amortized Cost	1,000,000	1,000,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 1,000,000	$ 1,000,000

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