PENSION AND POST-RETIREMENT PLANS - STATUS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension Benefits
Change in Benefit Obligation:
Benefit obligation at beginning of year	$ 263.1	$ 239.9
Service cost	4.8	5.1	$ 4.7
Interest cost	6.4	7.9	9.3
Actuarial (gain) loss	(10.7)	23.9
Benefits paid, net of subsidies received	(13.0)	(12.5)
Expenses paid	(1.1)	(1.2)
Benefit obligation at end of year	249.5	263.1	239.9
Change in Plan Assets:
Balance at the beginning of the period	212.8	194.8
Actual return on plan assets	31.2	22.7
Employer contribution	9.0	9.0	10.0
Benefits paid, net of subsidies received	(13.0)	(12.5)
Expenses paid	(1.1)	(1.2)
Balance at the end of the period	238.9	212.8	194.8
Funded Status and Recognized Liability	(10.6)	(50.3)
Post-retirement benefits
Change in Benefit Obligation:
Benefit obligation at beginning of year	29.1	26.0
Service cost	0.7	0.5	0.4
Interest cost	0.7	0.8	0.9
Participant contributions	0.8	0.8
Actuarial (gain) loss	0.1	2.7
Benefits paid, net of subsidies received	(2.1)	(1.7)
Benefit obligation at end of year	29.3	29.1	$ 26.0
Change in Plan Assets:
Participant contributions	0.8	0.8
Employer contribution	1.3	0.9
Benefits paid, net of subsidies received	(2.1)	(1.7)
Funded Status and Recognized Liability	(29.3)	(29.1)
Qualified Plan | Pension Benefits
Change in Benefit Obligation:
Benefit obligation at beginning of year	261.4
Benefit obligation at end of year	247.8	261.4
Change in Plan Assets:
Balance at the beginning of the period	210.0
Balance at the end of the period	$ 235.8	$ 210.0