INCOME TAXES - Effective income tax rate reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
INCOME TAXES
Tax at statutory rate	21.00%	21.00%	21.00%	21.00%
Nontaxable interest and dividends	(0.50%)	(0.40%)	(0.50%)	(0.40%)
Tax credits	(2.50%)	(1.60%)	(2.30%)	(1.70%)
State taxes	1.50%	1.90%	1.60%	1.70%
Other	0.20%	(0.40%)	0.70%	(0.10%)
Effective income tax rate reconciliation, percent, Total	19.70%	20.50%	20.50%	20.50%
Tax obligation under tax examinations				$ 4.0