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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

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