PENSION AND POST-RETIREMENT BENEFITS - Fair Value of Asset Categories (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 497.2	$ 464.0
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	313.3	303.2
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	183.9	160.8
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Group Annuity Contract [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	3.0
Group Annuity Contract [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Group Annuity Contract [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	3.0
Group Annuity Contract [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. small/mid cap equity [Member] | Common and Preferred Stock [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18.3	15.5
U.S. small/mid cap equity [Member] | Common and Preferred Stock [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18.3	15.5
U.S. small/mid cap equity [Member] | Common and Preferred Stock [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. small/mid cap equity [Member] | Common and Preferred Stock [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. small/mid cap equity [Member] | Common and Collective Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16.1	20.0
U.S. small/mid cap equity [Member] | Common and Collective Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16.1	20.0
U.S. small/mid cap equity [Member] | Common and Collective Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. small/mid cap equity [Member] | Common and Collective Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Corporate bonds [Member] | Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17.7	14.3
Corporate bonds [Member] | Mutual Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17.7	14.3
Corporate bonds [Member] | Mutual Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Corporate bonds [Member] | Mutual Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Corporate bonds [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	46.7	41.0
Corporate bonds [Member] | Fixed Income Securities [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Corporate bonds [Member] | Fixed Income Securities [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	46.7	41.0
Corporate bonds [Member] | Fixed Income Securities [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Corporate bonds [Member] | Common and Collective Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	51.5	56.0
Corporate bonds [Member] | Common and Collective Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	42.3	54.3
Corporate bonds [Member] | Common and Collective Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9.2	1.7
Corporate bonds [Member] | Common and Collective Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Corporate bonds [Member] | Hedge funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.3	4.5
Corporate bonds [Member] | Hedge funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Corporate bonds [Member] | Hedge funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10.3	4.5
Corporate bonds [Member] | Hedge funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Government bonds [Member] | Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8.4	11.9
Government bonds [Member] | Mutual Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8.4	11.9
Government bonds [Member] | Mutual Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Government bonds [Member] | Mutual Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Government bonds [Member] | Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15.4	13.9
Government bonds [Member] | Fixed Income Securities [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Government bonds [Member] | Fixed Income Securities [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15.4	13.9
Government bonds [Member] | Fixed Income Securities [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Government bonds [Member] | Common and Collective Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	55.3	68.4
Government bonds [Member] | Common and Collective Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	44.1	57.0
Government bonds [Member] | Common and Collective Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.2	11.4
Government bonds [Member] | Common and Collective Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Government bonds [Member] | Hedge funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.7	6.5
Government bonds [Member] | Hedge funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Government bonds [Member] | Hedge funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.7	6.5
Government bonds [Member] | Hedge funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. large cap equity [Member] | Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.1
U.S. large cap equity [Member] | Mutual Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.1	0.1
U.S. large cap equity [Member] | Mutual Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. large cap equity [Member] | Mutual Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. large cap equity [Member] | Common and Collective Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	78.6	68.8
U.S. large cap equity [Member] | Common and Collective Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	68.7	67.5
U.S. large cap equity [Member] | Common and Collective Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9.9	1.3
U.S. large cap equity [Member] | Common and Collective Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. large cap equity [Member] | Hedge funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.2	2.1
U.S. large cap equity [Member] | Hedge funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. large cap equity [Member] | Hedge funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.2	2.1
U.S. large cap equity [Member] | Hedge funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
International equities [Member] | Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.8	3.9
International equities [Member] | Mutual Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.8	3.9
International equities [Member] | Mutual Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
International equities [Member] | Mutual Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
International equities [Member] | Common and Collective Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	77.9	67.0
International equities [Member] | Common and Collective Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	42.8	34.9
International equities [Member] | Common and Collective Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	35.1	32.1
International equities [Member] | Common and Collective Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Emerging markets international equity [Member] | Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7.4	6.3
Emerging markets international equity [Member] | Mutual Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7.4	6.3
Emerging markets international equity [Member] | Mutual Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Emerging markets international equity [Member] | Mutual Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Emerging markets international equity [Member] | Common and Collective Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18.9	15.3
Emerging markets international equity [Member] | Common and Collective Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12.8	9.4
Emerging markets international equity [Member] | Common and Collective Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.1	5.9
Emerging markets international equity [Member] | Common and Collective Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Cash and cash equivalents [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8.2	10.6
Cash and cash equivalents [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8.2	10.6
Cash and cash equivalents [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Cash and cash equivalents [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Cash and cash equivalents [Member] | Common and Collective Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13.0	4.8
Cash and cash equivalents [Member] | Common and Collective Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13.0	4.8
Cash and cash equivalents [Member] | Common and Collective Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Cash and cash equivalents [Member] | Common and Collective Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Cash and cash equivalents [Member] | Hedge funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.3	2.4
Cash and cash equivalents [Member] | Hedge funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	3.3	0.0
Cash and cash equivalents [Member] | Hedge funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	2.4
Cash and cash equivalents [Member] | Hedge funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other [Member] | Mutual Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4.5	3.0
Other [Member] | Mutual Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4.5	3.0
Other [Member] | Mutual Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other [Member] | Mutual Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other [Member] | Common and Collective Funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.6	(7.2)
Other [Member] | Common and Collective Funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1.8	(10.3)
Other [Member] | Common and Collective Funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4.8	3.1
Other [Member] | Common and Collective Funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other [Member] | Hedge funds [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	33.3	31.9
Other [Member] | Hedge funds [Member] | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Other [Member] | Hedge funds [Member] | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	33.3	31.9
Other [Member] | Hedge funds [Member] | Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 0.0	$ 0.0