OPERATIONS AND SIGNIFICANT ACCOUNTING POLICIES - Other Income (Expense) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Other Income (Expense)
Total Other Income	$ 5.2	$ 5.9	$ 9.8	$ 14.5
Pension and Other Postretirement Benefit Plan Non-Service Credits
Other Income (Expense)
Total Other Income	1.5	3.7	3.3	8.0
Interest and Investment Income
Other Income (Expense)
Total Other Income	2.5	0.8	4.4	2.7
AFUDC - Equity
Other Income (Expense)
Total Other Income	1.3	1.3	2.7	2.5
Other Income (Expense)
Other Income (Expense)
Total Other Income	$ (0.1)	$ 0.1	$ (0.6)	$ 1.3