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ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME - Schedule of Accumulated Other Comprehensive (Loss) Income (Details) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pretax	$ 134	$ (575)
Income Taxes	(51)	130
Net of Income Taxes	83	(445)
Unrealized loss on securities available for sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pretax	(162)	(762)
Income Taxes	25	178
Net of Income Taxes	(137)	(584)
Unrealized loss on securities available for sale transferred to held to maturity
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pretax	(5)	(6)
Income Taxes	1	2
Net of Income Taxes	(4)	(4)
Defined benefit pension items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pretax	282	182
Income Taxes	(72)	(47)
Net of Income Taxes	210	135
Unrealized gain on cash flow hedge derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Pretax	19	11
Income Taxes	(5)	(3)
Net of Income Taxes	$ 14	$ 8

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