INVESTMENT SECURITIES - Schedule of Gross Unrealized Losses and Fair Value by Investment Category (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Fair Value
Less than 12 months	$ 2,988	$ 7,198
12 months or more	8,762	9,104
Total	11,750	16,302
Gross Unrealized Losses
Less than 12 months	(19)	(178)
12 months or more	(900)	(1,231)
Total	(919)	(1,409)
U.S. Treasury and agency obligations
Fair Value
Less than 12 months	1,270	2,343
12 months or more	710	456
Total	1,980	2,799
Gross Unrealized Losses
Less than 12 months	(9)	(68)
12 months or more	(31)	(42)
Total	(40)	(110)
Mortgage-backed securities
Fair Value
Less than 12 months	623	1,766
12 months or more	2,388	2,203
Total	3,011	3,969
Gross Unrealized Losses
Less than 12 months	(4)	(50)
12 months or more	(359)	(459)
Total	(363)	(509)
Tax-exempt municipal securities
Fair Value
Less than 12 months	64	97
12 months or more	354	405
Total	418	502
Gross Unrealized Losses
Less than 12 months	(1)	(1)
12 months or more	(16)	(21)
Total	(17)	(22)
Residential
Fair Value
Less than 12 months	7	130
12 months or more	331	343
Total	338	473
Gross Unrealized Losses
Less than 12 months	0	(2)
12 months or more	(49)	(62)
Total	(49)	(64)
Commercial
Fair Value
Less than 12 months	83	58
12 months or more	862	992
Total	945	1,050
Gross Unrealized Losses
Less than 12 months	0	(1)
12 months or more	(53)	(84)
Total	(53)	(85)
Asset-backed securities
Fair Value
Less than 12 months	153	419
12 months or more	278	436
Total	431	855
Gross Unrealized Losses
Less than 12 months	(2)	(5)
12 months or more	(11)	(19)
Total	(13)	(24)
Corporate debt securities
Fair Value
Less than 12 months	788	2,385
12 months or more	3,839	4,269
Total	4,627	6,654
Gross Unrealized Losses
Less than 12 months	(3)	(51)
12 months or more	(381)	(544)
Total	$ (384)	$ (595)