EMPLOYEE BENEFITS - Schedule of Fair Values of the Pension Plan Assets by Asset Category (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 284.5	$ 231.1
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	19.2	15.9
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	265.3	215.2
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.1	8.4
Cash and cash equivalents | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11.1	8.4
Cash and cash equivalents | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. large-cap
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38.1	37.2
U.S. large-cap | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. large-cap | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38.1	37.2
U.S. small-cap growth
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.5	4.9
U.S. small-cap growth | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
U.S. small-cap growth | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.5	4.9
Emerging markets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14.3	12.7
Emerging markets | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Emerging markets | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	14.3	12.7
Real estate investment trusts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.8	6.1
Real estate investment trusts | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Real estate investment trusts | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6.8	6.1
International large-cap value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48.2	45.1
International large-cap value | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8.1	7.5
International large-cap value | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	40.1	37.6
Hedge fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12.7	15.5
Hedge fund | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Hedge fund | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12.7	15.5
Government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48.1	40.2
Government bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Government bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	48.1	40.2
Corporate bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	94.7	55.5
Corporate bonds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Corporate bonds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	94.7	55.5
Emerging markets
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5.0	5.5
Emerging markets | Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0.0	0.0
Emerging markets | Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 5.0	$ 5.5