PENSION AND POST-RETIREMENT BENEFITS - Narrative (Details) $ in Millions	3 Months Ended			6 Months Ended		12 Months Ended
	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) plan	Jun. 30, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Retirement Benefits [Abstract]
Net periodic benefit cost	$ 1.5		$ 2.1	$ 2.7	$ 4.1		$ 7.2
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	1.5		2.1	2.7	4.1		$ 7.2
Aggregate employer contributions during 2020	19.0			19.0
Scenario, Forecast
Retirement Benefits [Abstract]
Net periodic benefit cost						$ 5.5
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost						$ 5.5
Pension Plans
Retirement Benefits [Abstract]
Net periodic benefit cost	1.3		2.0	2.3	3.8
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	1.3		2.0	2.3	3.8
Employer contributions	1.8			5.2
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	9.4			$ 9.4
Number of qualified plans | plan				2
Other Post-Retirement Benefit Plans
Retirement Benefits [Abstract]
Net periodic benefit cost	0.2		0.1	$ 0.4	0.3
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic benefit cost	0.2		$ 0.1	0.4	$ 0.3
Employer contributions	$ 0.1			$ 0.3