PENSION AND POST-RETIREMENT BENEFITS - Narrative (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021 USD ($) plan	Mar. 31, 2020 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	$ 1.3	$ 1.2		$ 4.0
Minimum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Aggregate employer contributions during 2021	21.0
Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Aggregate employer contributions during 2021	24.0
Forecast
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost			$ 5.0
Pension Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	1.1	1.0
Employer contributions	13.5
Pension Plans | Qualified Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer contributions		1.6
Employer contributions, expected deferral in 2020, CARES Act	$ 11.8
Number of qualified defined benefit plans | plan	2
Other Post-Retirement Benefit Plans
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	$ 0.2	$ 0.2
Employer contributions	$ 0.2