ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME - Schedule of Changes in Components of AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, shareholders' equity	$ 21,255	$ 9,662	$ 4,738
AOCI activity before reclassifications	45	224
Amounts reclassified from AOCI to earnings	1	20
Other comprehensive income (loss), net of tax	46	244	(745)
Ending balance, shareholders' equity	22,228	21,255	9,662
Total accumulated other comprehensive loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, shareholders' equity	(491)	(735)	10
Other comprehensive income (loss), net of tax	46	244	(745)
Ending balance, shareholders' equity	(445)	(491)	(735)
Unrealized loss on securities available for sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, shareholders' equity	(577)	(739)
AOCI activity before reclassifications	(7)	143
Amounts reclassified from AOCI to earnings	0	19
Other comprehensive income (loss), net of tax	(7)	162
Ending balance, shareholders' equity	(584)	(577)	(739)
Unrealized loss on securities available for sale transferred to held to maturity
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, shareholders' equity	(5)	(6)
AOCI activity before reclassifications	0	0
Amounts reclassified from AOCI to earnings	1	1
Other comprehensive income (loss), net of tax	1	1
Ending balance, shareholders' equity	(4)	(5)	(6)
Defined benefit pension items
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, shareholders' equity	91	10
AOCI activity before reclassifications	44	81
Amounts reclassified from AOCI to earnings	0	0
Other comprehensive income (loss), net of tax	44	81
Ending balance, shareholders' equity	135	91	10
Unrealized gain on cash flow hedge derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, shareholders' equity	0	0
AOCI activity before reclassifications	8	0
Amounts reclassified from AOCI to earnings	0	0
Other comprehensive income (loss), net of tax	8	0
Ending balance, shareholders' equity	$ 8	$ 0	$ 0