PENSION AND POST-RETIREMENT PLANS - STATUS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension Benefits
Change in Benefit Obligation:
Benefit obligation at beginning of year	$ 187.4	$ 249.5
Service cost	3.1	4.8	$ 4.8
Interest cost	10.0	7.0	6.4
Actuarial (gain) loss	5.5	(59.0)
Benefits paid, net of subsidies received	(12.9)	(14.1)
Expenses paid		(0.8)
Benefit obligation at end of year	193.1	187.4	249.5
Change in Plan Assets:
Balance at the beginning of the period	206.3	238.9
Actual return on plan assets	25.5	(26.7)
Employer contribution	9.0	9.0	9.0
Benefits paid, net of subsidies received	(12.9)	(14.1)
Expenses paid		(0.8)
Balance at the end of the period	227.9	206.3	238.9
Funded Status and Recognized Plan Assets and Benefit Obligations	34.8	18.9
Post-retirement benefits
Change in Benefit Obligation:
Benefit obligation at beginning of year	15.3	29.3
Service cost	0.2	0.7	0.7
Interest cost	0.8	0.8	0.7
Participant contributions	0.7	0.7
Actuarial (gain) loss	4.5	(14.2)
Benefits paid, net of subsidies received	(2.0)	(2.0)
Benefit obligation at end of year	19.5	15.3	$ 29.3
Change in Plan Assets:
Participant contributions	0.7	0.7
Employer contribution	1.3	1.3
Benefits paid, net of subsidies received	(2.0)	(2.0)
Funded Status and Recognized Plan Assets and Benefit Obligations	$ (19.5)	$ (15.3)