OTHER COMPREHENSIVE INCOME (Changes in Accumulated Other Comprehensive Income, Net of Tax) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, Beginning balance	$ (154.7)	$ (152.7)
Other comprehensive income (loss) before reclassifications	4.2	(6.5)	$ 13.4
Amounts reclassified from AOCI	6.7	4.5	15.2
Other comprehensive income (loss)	10.9	(2.0)	28.6
AOCI, Ending balance	(143.8)	(154.7)	(152.7)
Amortization Of Cash Flow Hedge Losses [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, Beginning balance	(21.0)	(22.5)
Other comprehensive income (loss) before reclassifications	0.0	0.0	0.0
Amounts reclassified from AOCI	1.6	1.5	1.5
Other comprehensive income (loss)	1.6	1.5	1.5
AOCI, Ending balance	(19.4)	(21.0)	(22.5)
Amortization Of Pension And Postretirement Plan Actuarial Loss And Prior Service Cost [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, Beginning balance	(133.7)	(130.2)
Other comprehensive income (loss) before reclassifications	4.2	(6.5)	13.4
Amounts reclassified from AOCI	5.1	3.0	13.7
Other comprehensive income (loss)	9.3	(3.5)	27.1
AOCI, Ending balance	$ (124.4)	$ (133.7)	(130.2)
Scenario, Previously Reported [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, Beginning balance			(181.3)
Scenario, Previously Reported [Member] | Amortization Of Cash Flow Hedge Losses [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, Beginning balance			(24.0)
Scenario, Previously Reported [Member] | Amortization Of Pension And Postretirement Plan Actuarial Loss And Prior Service Cost [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI, Beginning balance			$ (157.3)