INCOME TAXES (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Effective Income Tax Rate Reconciliation, Amount
Statutory federal income tax, amount	$ 14.2	$ 11.3	$ 33.6	$ 29.0
State income taxes net of federal tax benefit,amount	4.2	3.4	9.9	8.6
PTCs, net, amount	(4.1)	(3.1)	(9.9)	(7.1)
Federal excess deferred tax amortization, amount	(2.2)	(1.1)	(5.0)	(2.6)
ITCs, amount	(0.7)	(0.7)	(1.7)	(1.7)
Other, net, amount	0.9	0.4	1.9	0.7
Total income tax expense, amount	$ 12.3	$ 10.2	$ 28.8	$ 26.9
Effective Income Tax Rate Reconciliation, Percent
Statutory federal income tax, percent	21.00%	21.00%	21.00%	21.00%
State income taxes net of federal tax benefit, percent	6.30%	6.20%	6.20%	6.20%
PTCs, net, percent	(6.10%)	(5.80%)	(6.20%)	(5.20%)
Federal excess deferred tax amortization, percent	(3.20%)	(2.00%)	(3.10%)	(1.90%)
ITCs, percent	(1.10%)	(1.30%)	(1.10%)	(1.20%)
Other, net, percent	1.30%	0.80%	1.20%	0.60%
Total income tax expense, percent	18.20%	18.90%	18.00%	19.50%