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, 2024	Dec. 31, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, net amount	$ 45	$ 224
Amounts reclassified from AOCI to earnings, net amount	1	20
Other comprehensive (loss) income on securities available for sale and cash flow hedges, gross amount	62	330
Other comprehensive (loss) income on securities available for sale and cash flow hedges, tax	(16)	(86)
Other comprehensive income (loss), net of tax	46	244	$ (745)
Unrealized loss on securities available for sale:
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, gross amount	(10)	194
AOCI activity before reclassification, tax	3	(51)
AOCI activity before reclassification, net amount	(7)	143
Amounts reclassified from AOCI to earnings, gross amount	0	26
Amounts reclassified from AOCI to earnings, tax	0	(7)
Amounts reclassified from AOCI to earnings, net amount	0	19
Other comprehensive (loss) income on securities available for sale and cash flow hedges, gross amount	(10)	220
Other comprehensive (loss) income on securities available for sale and cash flow hedges, tax	3	(58)
Other comprehensive income (loss), net of tax	(7)	162
Unrealized loss on securities available for sale transferred to held to maturity
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, net amount	0	0
Amounts reclassified from AOCI to earnings, gross amount	1	1
Amounts reclassified from AOCI to earnings, tax	0	0
Amounts reclassified from AOCI to earnings, net amount	1	1
Other comprehensive (loss) income on securities available for sale and cash flow hedges, gross amount	1	1
Other comprehensive (loss) income on securities available for sale and cash flow hedges, tax	0	0
Other comprehensive income (loss), net of tax	1	1
Defined benefit pension items
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, gross amount	60	109
AOCI activity before reclassification, tax	(16)	(28)
AOCI activity before reclassification, net amount	44	81
Amounts reclassified from AOCI to earnings, net amount	0	0
Other comprehensive income (loss), net of tax	44	81
Unrealized gain on cash flow hedge derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, gross amount	11	0
AOCI activity before reclassification, tax	(3)	0
AOCI activity before reclassification, net amount	8	0
Amounts reclassified from AOCI to earnings, gross amount	0	0
Amounts reclassified from AOCI to earnings, tax	0	0
Amounts reclassified from AOCI to earnings, net amount	0	0
Other comprehensive (loss) income on securities available for sale and cash flow hedges, gross amount	11	0
Other comprehensive (loss) income on securities available for sale and cash flow hedges, tax	(3)	0
Other comprehensive income (loss), net of tax	$ 8	$ 0

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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