ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME - Schedule of Pretax and After-tax Components of Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) on securities available for sale and cash flow hedges, gross amount	$ 114	$ (37)	$ 445	$ (161)
Other comprehensive income (loss) on securities available for sale and cash flow hedges, tax	(29)	9	(114)	42
Other comprehensive income (loss), net of tax	85	(28)	331	(119)
AOCI activity before reclassification, net amount			334
Amounts reclassified from AOCI to earnings, net amount			(3)
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, gross amount	119	(30)	441	(154)
Other comprehensive income (loss) on securities available for sale and cash flow hedges, tax	(30)	8	(113)	41
Other comprehensive income (loss), net of tax	89	(22)	328	(113)
Defined benefit pension items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) on securities available for sale and cash flow hedges, gross amount	(4)	(10)	(4)	(10)
Other comprehensive income (loss) on securities available for sale and cash flow hedges, tax	1	2	1	2
Other comprehensive income (loss), net of tax	(3)	(8)	(3)	(8)
AOCI activity before reclassification, net amount			(3)
Amounts reclassified from AOCI to earnings, net amount			0
Unrealized gain on cash flow hedge derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss) on securities available for sale and cash flow hedges, gross amount	(1)	3	8	3
Other comprehensive income (loss) on securities available for sale and cash flow hedges, tax	0	(1)	(2)	(1)
Other comprehensive income (loss), net of tax	(1)	2	6	2
AOCI activity before reclassification, gross amount	0	3	12	3
AOCI activity before reclassification, tax	(1)	(1)	(3)	(1)
AOCI activity before reclassification, net amount	(1)	2	9	2
Amounts reclassified from AOCI to earnings, gross amount	(1)	0	(4)	0
Amounts reclassified from AOCI to earnings, tax	1	0	1	0
Amounts reclassified from AOCI to earnings, net amount	$ 0	$ 0	$ (3)	$ 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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