INCOME TAX EXPENSE - Schedule of Income Tax Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Current Income Tax Expense
Federal	$ 3.3	$ 3.0	$ 6.8	$ 8.6
State	3.2	3.2	6.6	5.4
Total Current Income Tax Expense	6.5	6.2	13.4	14.0
Deferred Income Tax Expense (Benefit)
Federal	(5.0)	(7.8)	(10.0)	(16.1)
State	0.1	1.3	2.5	3.4
Investment Tax Credit Amortization	(0.2)	(0.1)	(0.5)	(0.2)
Total Deferred Income Tax Benefit	(5.1)	(6.6)	(8.0)	(12.9)
Total Income Tax Expense (Benefit)	$ 1.4	$ (0.4)	$ 5.4	$ 1.1