Investment Securities - Summary of Investment Securities (Details) - USD ($)	Jun. 30, 2022	Dec. 31, 2021
Available-for-sale securities
Amortized Cost	$ 2,500,000,000	$ 1,788,000,000
Gross Unrealized Gains	0	20,000,000
Gross Unrealized Losses	(154,000,000)	(4,000,000)
Fair Value	2,346,000,000	1,804,000,000
Held-to-maturity securities
Amortized Cost	173,000,000	205,000,000
Gross Unrealized Gains	0	4,000,000
Gross Unrealized Losses	(7,000,000)	0
Fair Value	166,000,000	209,000,000
Securities of a single issuer that exceeded 10% of stockholders' equity	0	0
Agency - Commercial
Available-for-sale securities
Amortized Cost	1,560,000,000	739,000,000
Gross Unrealized Gains	0	8,000,000
Gross Unrealized Losses	(74,000,000)	0
Fair Value	1,486,000,000	747,000,000
Held-to-maturity securities
Amortized Cost	84,000,000	99,000,000
Gross Unrealized Gains	0	1,000,000
Gross Unrealized Losses	(3,000,000)	0
Fair Value	81,000,000	100,000,000
Agency - Residential
Available-for-sale securities
Amortized Cost	614,000,000	690,000,000
Gross Unrealized Gains	0	9,000,000
Gross Unrealized Losses	(53,000,000)	(3,000,000)
Fair Value	561,000,000	696,000,000
Held-to-maturity securities
Amortized Cost	89,000,000	106,000,000
Gross Unrealized Gains	0	3,000,000
Gross Unrealized Losses	(4,000,000)	0
Fair Value	85,000,000	109,000,000
Corporate debt obligations
Available-for-sale securities
Amortized Cost	57,000,000	70,000,000
Gross Unrealized Gains	0	3,000,000
Gross Unrealized Losses	0	0
Fair Value	57,000,000	73,000,000
Municipal obligations
Available-for-sale securities
Amortized Cost	17,000,000	20,000,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,000,000)	0
Fair Value	16,000,000	20,000,000
Other MBS
Available-for-sale securities
Amortized Cost	251,000,000	268,000,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(26,000,000)	(1,000,000)
Fair Value	225,000,000	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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