Investment Securities - Schedule of Amortized Cost and Fair Value of Investment Securities (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Investment securities available for sale
Amortized Cost	$ 17,836	$ 9,967
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(1,175)	(973)
Investment securities available for sale	16,661	8,995
Investment in marketable equity securities
Amortized Cost	75	75
Gross Unrealized Gains	11	21
Gross Unrealized Losses	(11)	(1)
Fair Value	75	95
Investment securities held to maturity
Amortized Cost	10,082	10,279
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,930)	(1,484)
Fair Value	8,152	8,795
Total investment securities
Amortized Cost	27,993	20,321
Gross Unrealized Gains	11	22
Gross Unrealized Losses	(3,116)	(2,458)
Fair Value	24,888	17,885
U.S. Treasury
Investment securities available for sale
Amortized Cost	8,765	2,035
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(118)	(137)
Investment securities available for sale	8,647	1,898
Investment securities held to maturity
Amortized Cost	478	474
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(53)	(50)
Fair Value	425	424
Government agency
Investment securities available for sale
Amortized Cost	132	164
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(3)	(2)
Investment securities available for sale	129	162
Investment securities held to maturity
Amortized Cost	1,504	1,548
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(196)	(186)
Fair Value	1,308	1,362
Residential mortgage-backed securities
Investment securities available for sale
Amortized Cost	6,352	5,424
Gross Unrealized Gains	0	1
Gross Unrealized Losses	(752)	(630)
Investment securities available for sale	5,600	4,795
Investment securities held to maturity
Amortized Cost	4,296	4,605
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(866)	(723)
Fair Value	3,430	3,882
Commercial mortgage-backed securities
Investment securities available for sale
Amortized Cost	2,042	1,774
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(245)	(170)
Investment securities available for sale	1,797	1,604
Investment securities held to maturity
Amortized Cost	3,505	3,355
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(769)	(484)
Fair Value	2,736	2,871
Corporate bonds
Investment securities available for sale
Amortized Cost	535	570
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(57)	(34)
Investment securities available for sale	478	536
Municipal bonds
Investment securities available for sale
Amortized Cost	10
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Investment securities available for sale	10
Supranational securities
Investment securities held to maturity
Amortized Cost	297	295
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(46)	(41)
Fair Value	251	254
Other
Investment securities held to maturity
Amortized Cost	2	2
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	$ 2	$ 2

Equity Securities FV-NI, Accumulated Gross Unrealized Gain, before Tax

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