INCOME TAXES - Effective Income Tax Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Amount
U.S. Federal income tax expense	$ 396	$ 426	$ 558
Increase (decrease) resulting from:
State and local income taxes (net of federal benefit)	46	58	133
Bank-owned life insurance	(22)	(20)	(19)
Tax-exempt interest	(12)	(12)	(8)
Tax advantaged investments (including related credits)	(82)	(77)	(102)
Other tax credits	(2)	(3)	(9)
Adjustments for uncertain tax positions	0	5	1
Non-deductible FDIC insurance premiums	34	35	20
Legacy tax matters	0	0	3
Other	21	10	5
Income tax expense	$ 379	$ 422	$ 582
Rate
U.S. Federal income tax rate	21.00%	21.00%	21.00%
Increase (decrease) resulting from:
State and local income taxes (net of federal benefit)	2.50%	2.90%	5.00%
Bank-owned life insurance	(1.20%)	(1.00%)	(0.70%)
Tax-exempt interest	(0.70%)	(0.60%)	(0.30%)
Tax advantaged investments (including related credits)	(4.40%)	(3.80%)	(3.80%)
Other tax credits	(0.10%)	(0.10%)	(0.30%)
Adjustments for uncertain tax positions	0.00%	0.20%	0.00%
Non-deductible FDIC insurance premiums	1.80%	1.70%	0.70%
Legacy tax matters	0.00%	0.00%	0.10%
Other	1.20%	0.50%	0.20%
Total income tax expense and effective tax rate	20.10%	20.80%	21.90%