OTHER COMPREHENSIVE INCOME - Activity/Roll Forward (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
After-tax
Other comprehensive income (loss), net of tax	$ 958	$ (190)	$ 422
Unrealized gains and (losses) on debt securities
Pretax
Unrealized gains (losses) on available-for-sale securities arising during the period, net of hedges	749	(454)	154
Reclassification from AOCI, before tax	71	94	47
Tax (expense) benefit
OCI before reclassification, tax	(176)	107	(36)
Reclassification adjustment for realized net losses included in net income	(17)	(18)	(11)
After-tax
Unrealized gains (losses) on available-for-sale securities arising during the period, net of hedges	573	(347)	118
Reclassification adjustment for realized net losses included in net income	54	76	36
Net change related to cash flow hedges on loans
Pretax
Unrealized gains (losses) on available-for-sale securities arising during the period, net of hedges	332	(111)	162
Reclassification from AOCI, before tax	52	236	187
Tax (expense) benefit
OCI before reclassification, tax	(78)	26	(37)
Reclassification adjustment for realized net losses included in net income	(12)	(55)	(43)
After-tax
Unrealized gains (losses) on available-for-sale securities arising during the period, net of hedges	254	(85)	125
Reclassification adjustment for realized net losses included in net income	40	181	144
Net change related to cash flow hedges on loans | Cash Flow Hedges
Pretax
Total other comprehensive income (loss), pretax	384	125	349
Tax (expense) benefit
Total other comprehensive income (loss), tax (expense) benefit	(90)	(29)	(80)
After-tax
Other comprehensive income (loss), net of tax	294	96	269
Accumulated foreign currency adjustment
Pretax
Unrealized gains (losses) on available-for-sale securities arising during the period, net of hedges	9	(6)	2
Tax (expense) benefit
OCI before reclassification, tax	(1)	0	0
After-tax
Unrealized gains (losses) on available-for-sale securities arising during the period, net of hedges	8	(6)	2
Unrealized losses for pension and other post-retirement obligations
Pretax
Unrealized gains (losses) on available-for-sale securities arising during the period, net of hedges	38	(12)	(4)
Tax (expense) benefit
OCI before reclassification, tax	(9)	3	1
After-tax
Unrealized gains (losses) on available-for-sale securities arising during the period, net of hedges	29	(9)	(3)
AOCI
Pretax
Total other comprehensive income (loss), pretax	1,251	(253)	548
Tax (expense) benefit
Total other comprehensive income (loss), tax (expense) benefit	(293)	63	(126)
After-tax
Other comprehensive income (loss), net of tax	958	(190)	422
Debt securities | Unrealized gains and (losses) on debt securities
Pretax
Total other comprehensive income (loss), pretax	820	(360)	201
Tax (expense) benefit
Total other comprehensive income (loss), tax (expense) benefit	(193)	89	(47)
After-tax
Other comprehensive income (loss), net of tax	$ 627	$ (271)	$ 154