ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 26,317	$ 24,254
Other comprehensive income (loss) before reclassifications	(224)	490
Amounts reclassified from AOCI to earnings	106	164
Total other comprehensive income (loss), net	(118)	654
Ending balance	26,172	24,866
Total AOCI
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(1,970)	(3,595)
Total other comprehensive income (loss), net	(118)	654
Ending balance	(2,088)	(2,941)
Net Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(118)	(925)
Other comprehensive income (loss) before reclassifications	(124)	208
Amounts reclassified from AOCI to earnings	83	148
Total other comprehensive income (loss), net	(41)	356
Ending balance	(159)	(569)
Net Unrealized Gains (Losses) on Investment Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(1,603)	(2,369)
Other comprehensive income (loss) before reclassifications	(100)	282
Amounts reclassified from AOCI to earnings	19	13
Total other comprehensive income (loss), net	(81)	295
Ending balance	(1,684)	(2,074)
Defined Benefit Plans
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(249)	(301)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from AOCI to earnings	4	3
Total other comprehensive income (loss), net	4	3
Ending balance	$ (245)	$ (298)