EMPLOYEE BENEFIT PLANS - PENSION AND OTHER POSTRETIREMENT PLAN ASSETS (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Pension Plan Assets
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	$ 904.7	$ 846.6
401(h) other benefit plan assets invested as pension assets	(8.8)	(8.2)
Total	895.9	838.4
Pension Plan Assets | Cash and cash equivalents
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	24.9	20.8
Pension Plan Assets | United States equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	251.4	294.0
Pension Plan Assets | International equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	280.3	292.8
Pension Plan Assets | United States government
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	54.0	50.4
Pension Plan Assets | Foreign government debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	12.1	10.4
Pension Plan Assets | Corporate debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	250.5	135.5
Pension Plan Assets | Asset-backed securities
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets		33.3
Pension Plan Assets | Other
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	31.5	9.4
Pension Plan Assets | Level 1
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	149.3	116.7
401(h) other benefit plan assets invested as pension assets	(1.5)	(1.1)
Total	147.8	115.6
Pension Plan Assets | Level 1 | Cash and cash equivalents
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	1.1
Pension Plan Assets | Level 1 | United States equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	53.6	54.1
Pension Plan Assets | Level 1 | International equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	54.4	61.5
Pension Plan Assets | Level 1 | United States government
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	41.3	0
Pension Plan Assets | Level 1 | Foreign government debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Pension Plan Assets | Level 1 | Corporate debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Pension Plan Assets | Level 1 | Asset-backed securities
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets		0
Pension Plan Assets | Level 1 | Other
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Pension Plan Assets | Level 2
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	755.4	727.9
401(h) other benefit plan assets invested as pension assets	(7.3)	(7.1)
Total	748.1	720.8
Pension Plan Assets | Level 2 | Cash and cash equivalents
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	24.9	19.7
Pension Plan Assets | Level 2 | United States equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	197.8	239.9
Pension Plan Assets | Level 2 | International equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	225.9	231.3
Pension Plan Assets | Level 2 | United States government
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	12.7	50.4
Pension Plan Assets | Level 2 | Foreign government debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	12.1	9.1
Pension Plan Assets | Level 2 | Corporate debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	250.5	134.8
Pension Plan Assets | Level 2 | Asset-backed securities
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets		33.3
Pension Plan Assets | Level 2 | Other
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	31.5	9.4
Pension Plan Assets | Level 3
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	2.0	2.7
401(h) other benefit plan assets invested as pension assets	0	0
Total	0	2.0
Pension Plan Assets | Level 3 | Cash and cash equivalents
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Pension Plan Assets | Level 3 | United States equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Pension Plan Assets | Level 3 | International equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Pension Plan Assets | Level 3 | United States government
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Pension Plan Assets | Level 3 | Foreign government debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	1.3	2.2
Pension Plan Assets | Level 3 | Corporate debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0.7	0.5
Pension Plan Assets | Level 3 | Asset-backed securities
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets		0
Pension Plan Assets | Level 3 | Other
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Other Benefit Plan Assets
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	227.9	228.5
401(h) other benefit plan assets invested as pension assets	8.8	8.2
Total	236.7	236.7
Other Benefit Plan Assets | Cash and cash equivalents
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	6.2	2.3
Other Benefit Plan Assets | United States equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	77.2	80.7
Other Benefit Plan Assets | International equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	83.0	80.0
Other Benefit Plan Assets | United States government
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	61.3	65.6
Other Benefit Plan Assets | Foreign government debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Other Benefit Plan Assets | Corporate debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Other Benefit Plan Assets | Asset-backed securities
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets		0
Other Benefit Plan Assets | Other
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0.2	(0.1)
Other Benefit Plan Assets | Level 1
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	98.5	95.8
401(h) other benefit plan assets invested as pension assets	1.5	1.1
Total	100.0	96.9
Other Benefit Plan Assets | Level 1 | Cash and cash equivalents
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	4.6	0
Other Benefit Plan Assets | Level 1 | United States equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	14.8	14.2
Other Benefit Plan Assets | Level 1 | International equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	17.6	16.7
Other Benefit Plan Assets | Level 1 | United States government
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	61.3	65.0
Other Benefit Plan Assets | Level 1 | Foreign government debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Other Benefit Plan Assets | Level 1 | Corporate debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Other Benefit Plan Assets | Level 1 | Asset-backed securities
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets		0
Other Benefit Plan Assets | Level 1 | Other
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0.2	(0.1)
Other Benefit Plan Assets | Level 2
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	129.4	132.7
401(h) other benefit plan assets invested as pension assets	7.3	7.1
Total	136.7	139.8
Other Benefit Plan Assets | Level 2 | Cash and cash equivalents
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	1.6	2.3
Other Benefit Plan Assets | Level 2 | United States equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	62.4	66.5
Other Benefit Plan Assets | Level 2 | International equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	65.4	63.3
Other Benefit Plan Assets | Level 2 | United States government
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0.6
Other Benefit Plan Assets | Level 2 | Foreign government debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Other Benefit Plan Assets | Level 2 | Corporate debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Other Benefit Plan Assets | Level 2 | Asset-backed securities
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets		0
Other Benefit Plan Assets | Level 2 | Other
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Other Benefit Plan Assets | Level 3
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
401(h) other benefit plan assets invested as pension assets	0	0
Total	0	0
Other Benefit Plan Assets | Level 3 | Cash and cash equivalents
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Other Benefit Plan Assets | Level 3 | United States equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Other Benefit Plan Assets | Level 3 | International equity
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Other Benefit Plan Assets | Level 3 | United States government
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Other Benefit Plan Assets | Level 3 | Foreign government debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Other Benefit Plan Assets | Level 3 | Corporate debt
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	0	0
Other Benefit Plan Assets | Level 3 | Asset-backed securities
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets		0
Other Benefit Plan Assets | Level 3 | Other
Investments recorded at fair value, by asset class
Fair value of plan assets before the adjustment for 401(h) other benefit plan assets invested as pension assets	$ 0	$ 0