PENSIONS AND OTHER POSTRETIREMENT BENEFITS - Pension and Other Postretirement Benefits (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Pension Plan [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	$ 5.3	$ 4.2	$ 10.6	$ 8.3
Interest cost	14.9	8.6	23.1	17.3
Expected return on plan assets	(36.7)	(13.7)	(55.2)	(27.3)
Prior service cost (credits)	0.3	0.3	0.5	0.6
Net actuarial loss	6.6	5.9	13.3	11.8
Net periodic benefit cost (credit)	(9.6)	5.3	(7.7)	10.7
Defined Benefit Pension Contributions	0.2	3.5	4.0	6.7
Other Postretirement Benefit Plans, Defined Benefit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	1.4	0.4	1.9	0.8
Interest cost	4.3	2.4	6.5	4.7
Expected return on plan assets	(4.6)	(4.2)	(9.1)	(8.4)
Prior service cost (credits)	(0.5)	(0.5)	(1.0)	(1.0)
Net actuarial loss	0.7	1.2	1.4	2.5
Net periodic benefit cost (credit)	1.3	(0.7)	(0.3)	(1.4)
OPEB Contributions	$ 0.0	$ 0.0	$ 0.0	$ 0.0