ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME - Schedule of Pretax and After-tax Components of Other Comprehensive Income (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, Net of Income Taxes	$ 533	$ 45
Amounts reclassified from AOCI to earnings, Net of Income Taxes	(5)	1
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Pretax	709	62
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Income Taxes	(181)	(16)
Other comprehensive income, net of tax	528	46	$ 244
Unrealized loss on securities available for sale:
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, Pretax	603	(10)
AOCI activity before reclassification, Income Taxes	(154)	3
AOCI activity before reclassification, Net of Income Taxes	449	(7)
Amounts reclassified from AOCI to earnings, Pretax	(3)	0
Amounts reclassified from AOCI to earnings, Income Taxes	1	0
Amounts reclassified from AOCI to earnings, Net of Income Taxes	(2)	0
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Pretax	600	(10)
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Income Taxes	(153)	3
Other comprehensive income, net of tax	447	(7)
Unrealized loss on securities available for sale transferred to held to maturity
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, Net of Income Taxes	0	0
Amounts reclassified from AOCI to earnings, Pretax	1	1
Amounts reclassified from AOCI to earnings, Income Taxes	(1)	0
Amounts reclassified from AOCI to earnings, Net of Income Taxes	0	1
Other comprehensive income, net of tax	0	1
Defined benefit pension items
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, Net of Income Taxes	75	44
Amounts reclassified from AOCI to earnings, Net of Income Taxes	0	0
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Pretax	100	60
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Income Taxes	(25)	(16)
Other comprehensive income, net of tax	75	44
Unrealized gain on cash flow hedge derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, Pretax	12	11
AOCI activity before reclassification, Income Taxes	(3)	(3)
AOCI activity before reclassification, Net of Income Taxes	9	8
Amounts reclassified from AOCI to earnings, Pretax	(4)	0
Amounts reclassified from AOCI to earnings, Income Taxes	1	0
Amounts reclassified from AOCI to earnings, Net of Income Taxes	(3)	0
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Pretax	8	11
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Income Taxes	(2)	(3)
Other comprehensive income, net of tax	$ 6	$ 8

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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