EMPLOYEE BENEFIT PLANS - PENSION AND OTHER POSTRETIREMENT BENEFIT 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	$ 1,537.5	$ 1,570.6
401(h) other benefit plan assets invested as pension assets	(44.6)	(44.1)
Total	1,492.9	1,526.5
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	42.3	38.6
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	427.2	545.5
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	476.3	543.1
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	91.9	93.6
Pension Plan Assets | Foreign 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	20.6	19.3
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	425.7	251.3
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		61.8
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	53.5	17.4
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	253.7	216.5
401(h) other benefit plan assets invested as pension assets	(7.4)	(6.1)
Total	246.3	210.4
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	2.0
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	91.0	100.4
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	92.4	114.1
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	70.3	0
Pension Plan Assets | Level 1 | Foreign 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 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	1,283.8	1,350.4
401(h) other benefit plan assets invested as pension assets	(37.2)	(37.9)
Total	1,246.6	1,312.5
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	42.3	36.6
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	336.2	445.1
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	383.9	429.0
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	21.6	93.6
Pension Plan Assets | Level 2 | Foreign 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	20.6	16.9
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	425.7	250.0
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		61.8
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	53.5	17.4
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	3.7	5.2
401(h) other benefit plan assets invested as pension assets	0	(0.1)
Total	0	3.6
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
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	2.4	4.1
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	1.3	1.0
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	0.1
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	403.1	425.5
401(h) other benefit plan assets invested as pension assets	44.6	44.1
Total	447.7	469.6
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	11.1	4.0
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	143.4	153.6
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	136.5	145.0
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	111.1	121.9
Other Benefit Plan Assets | Foreign 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 | 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	1.0	1.0
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	159.9	163.1
401(h) other benefit plan assets invested as pension assets	7.4	6.1
Total	167.3	169.2
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	8.5	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	20.6	21.4
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	18.7	19.5
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	111.1	121.2
Other Benefit Plan Assets | Level 1 | Foreign 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 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	1.0	1.0
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	243.2	262.4
401(h) other benefit plan assets invested as pension assets	37.2	37.9
Total	280.4	300.3
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	2.6	4.0
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	122.8	132.2
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	117.8	125.5
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	0.7
Other Benefit Plan Assets | Level 2 | Foreign 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 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	0.1
Total	0	0.1
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
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