ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME - Schedule of Pretax and After-tax Components of Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, Net of Income Taxes	$ (155)	$ 249
Amounts reclassified from AOCI to earnings, Net of Income Taxes	0	(3)
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Pretax	(208)	331
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Income Taxes	53	(85)
Other comprehensive (loss) income, net of tax	(155)	246
Unrealized loss on securities available for sale:
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Pretax	(187)	322
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Income Taxes	48	(83)
Other comprehensive (loss) income, net of tax	(139)	239
Defined benefit pension items
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, Net of Income Taxes	(2)	0
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	(2)	0
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Income Taxes	0	0
Other comprehensive (loss) income, net of tax	(2)	0
Unrealized gain on cash flow hedge derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, Pretax	(19)	12
AOCI activity before reclassification, Income Taxes	5	(2)
AOCI activity before reclassification, Net of Income Taxes	(14)	10
Amounts reclassified from AOCI to earnings, Pretax	0	(3)
Amounts reclassified from AOCI to earnings, Income Taxes	0	0
Amounts reclassified from AOCI to earnings, Net of Income Taxes	0	(3)
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Pretax	(19)	9
Other comprehensive income (loss) on securities available for sale and cash flow hedges, Income Taxes	5	(2)
Other comprehensive (loss) income, net of tax	$ (14)	$ 7

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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