INCOME TAXES - Effective Income Tax Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Amount
U.S. Federal income tax expense	$ 426	$ 558	$ 625
Increase (decrease) resulting from:
State and local income taxes (net of federal benefit)	58	133	126
Bank-owned life insurance	(20)	(19)	(14)
Tax-exempt interest	(12)	(8)	(7)
Tax advantaged investments (including related credits)	(77)	(102)	(95)
Other tax credits	(3)	(9)	(7)
Adjustments for uncertain tax positions	5	1	3
Non-deductible FDIC insurance premiums	35	20	14
Legacy tax matters	0	3	0
Other	10	5	13
Income tax expense	$ 422	$ 582	$ 658
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)	2.90%	5.00%	4.20%
Bank-owned life insurance	(1.00%)	(0.70%)	(0.50%)
Tax-exempt interest	(0.60%)	(0.30%)	(0.20%)
Tax advantaged investments (including related credits)	(3.80%)	(3.80%)	(3.20%)
Other tax credits	(0.10%)	(0.30%)	(0.20%)
Adjustments for uncertain tax positions	0.20%	0.00%	0.10%
Non-deductible FDIC insurance premiums	1.70%	0.70%	0.50%
Legacy tax matters	0.00%	0.10%	0.00%
Other	0.50%	0.20%	0.40%
Total income tax expense and effective tax rate	20.80%	21.90%	22.10%