INCOME TAXES - Effective Income Tax Reconciliation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Amount
U.S. Federal income tax expense	$ 558	$ 625	$ 273
Increase (decrease) resulting from:
State and local income taxes (net of federal benefit)	133	126	54
Bank-owned life insurance	(19)	(14)	(12)
Tax-exempt interest	(8)	(7)	(10)
Tax advantaged investments (including related credits)	(102)	(95)	(68)
Other tax credits	(9)	(7)	(6)
Adjustments for uncertain tax positions	1	3	(1)
Non-deductible FDIC premiums	20	14	14
Legacy tax matters	3	0	(4)
Other	5	13	1
Income tax expense	$ 582	$ 658	$ 241
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)	5.00%	4.20%	4.20%
Bank-owned life insurance	(0.70%)	(0.50%)	(0.90%)
Tax-exempt interest	(0.30%)	(0.20%)	(0.70%)
Tax advantaged investments (including related credits)	(3.80%)	(3.20%)	(5.30%)
Other tax credits	(0.30%)	(0.20%)	(0.50%)
Adjustments for uncertain tax positions	0.00%	0.10%	(0.10%)
Non-deductible FDIC premiums	0.70%	0.50%	1.10%
Legacy tax matters	0.10%	0.00%	(0.30%)
Other	0.20%	0.40%	0.00%
Total income tax expense and tax rate	21.90%	22.10%	18.50%