ACCUMULATED OTHER COMPREHENSIVE (LOSS) INCOME - Schedule of Changes in Components of AOCI (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, shareholders' equity	$ 21,255	$ 9,662
AOCI activity before reclassifications	(91)	53
Amounts reclassified from AOCI to earnings	0	13
Other comprehensive (loss) income, net of tax	(91)	66
Ending balance, shareholders' equity	21,848	19,216
Total accumulated other comprehensive (loss) income
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance, shareholders' equity	(491)	(735)
Other comprehensive (loss) income, net of tax	(91)	66
Ending balance, shareholders' equity	(582)	(669)
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	(91)	45
Amounts reclassified from AOCI to earnings	0	13
Other comprehensive (loss) income, net of tax	(91)	58
Ending balance, shareholders' equity	(668)	(681)
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	0	0
Other comprehensive (loss) income, net of tax	0	0
Ending balance, shareholders' equity	(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	0	8
Amounts reclassified from AOCI to earnings	0	0
Other comprehensive (loss) income, net of tax	0	8
Ending balance, shareholders' equity	$ 91	$ 18