ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME - Schedule of Pretax and After-tax Components of Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, Net of Income Taxes			$ (874)	$ 404
Amounts reclassified from AOCI to earnings, Net of Income Taxes			(5)	(3)
Other comprehensive (loss) income on securities available for sale and cash flow hedges, Pretax	$ (760)	$ 95	(1,180)	540
Other comprehensive (loss) income on securities available for sale and cash flow hedges, Income Taxes	194	(25)	301	(139)
Other comprehensive income (loss) for the period	(566)	70	(879)	401
Unrealized (loss) gain on securities available for sale:
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, Pretax	(693)	97	(1,058)	538
AOCI activity before reclassification, Income Taxes	177	(25)	270	(138)
AOCI activity before reclassification, Net of Income Taxes	(516)	72	(788)	400
Amounts reclassified from AOCI to earnings, Pretax	(1)	0	(1)	0
Amounts reclassified from AOCI to earnings, Income Taxes	0	0	0	0
Amounts reclassified from AOCI to earnings, Net of Income Taxes	(1)	0	(1)	0
Other comprehensive (loss) income on securities available for sale and cash flow hedges, Pretax	(694)	97	(1,059)	538
Other comprehensive (loss) income on securities available for sale and cash flow hedges, Income Taxes	177	(25)	270	(138)
Other comprehensive income (loss) for the period	(517)	72	(789)	400
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	0	1	0	1
Amounts reclassified from AOCI to earnings, Income Taxes	0	(1)	0	(1)
Amounts reclassified from AOCI to earnings, Net of Income Taxes	0	0	0	0
Other comprehensive income (loss) for the period			0	0
Defined benefit pension items
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, Pretax			(5)	(5)
AOCI activity before reclassification, Income Taxes			1	1
AOCI activity before reclassification, Net of Income Taxes			(4)	(4)
Amounts reclassified from AOCI to earnings, Pretax			(1)	0
Amounts reclassified from AOCI to earnings, Income Taxes			0	0
Amounts reclassified from AOCI to earnings, Net of Income Taxes			(1)	0
Other comprehensive (loss) income on securities available for sale and cash flow hedges, Pretax	0	(1)	(6)	(5)
Other comprehensive (loss) income on securities available for sale and cash flow hedges, Income Taxes	0	0	1	1
Other comprehensive income (loss) for the period	0	(1)	(5)	(4)
Unrealized gain (loss) on cash flow hedge derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI activity before reclassification, Pretax	(64)	(2)	(111)	10
AOCI activity before reclassification, Income Taxes	16	1	29	(2)
AOCI activity before reclassification, Net of Income Taxes	(48)	(1)	(82)	8
Amounts reclassified from AOCI to earnings, Pretax	(2)	0	(4)	(4)
Amounts reclassified from AOCI to earnings, Income Taxes	1	0	1	1
Amounts reclassified from AOCI to earnings, Net of Income Taxes	(1)	0	(3)	(3)
Other comprehensive (loss) income on securities available for sale and cash flow hedges, Pretax	(66)	(2)	(115)	6
Other comprehensive (loss) income on securities available for sale and cash flow hedges, Income Taxes	17	1	30	(1)
Other comprehensive income (loss) for the period	$ (49)	$ (1)	$ (85)	$ 5

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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