PENSION AND POST-RETIREMENT BENEFITS - Components of Net Periodic Benefit Costs (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Net periodic benefit (income) costs:
Defined Benefit Plan, Net Periodic Benefit Cost	$ (0.3)	$ (1.4)	$ (1.6)	$ (4.0)	$ (5.4)
Pension Plan [Member]
Net periodic benefit (income) costs:
Defined Benefit Plan, Service Cost	0.2	0.2	0.6	0.6
Defined Benefit Plan, Interest Cost	7.2	7.5	21.5	22.6
Defined Benefit Plan, Expected Return on Plan Assets	(10.0)	(10.3)	(30.3)	(31.0)
Amortization of actuarial loss	2.2	1.1	6.3	3.3
Defined Benefit Plan Net Periodic Benefit Cost Before Portion Allocated To Affiliate	(0.4)	(1.5)	(1.9)	(4.5)
Defined Benefit Plan Net Periodic Benefit Cost Portion Allocated To Affiliate	0.0	(0.1)	(0.1)	(0.1)
Defined Benefit Plan, Net Periodic Benefit Cost	(0.4)	(1.6)	(2.0)	(4.6)
Other Postretirement Benefit Plan [Member]
Net periodic benefit (income) costs:
Defined Benefit Plan, Service Cost	0.0	0.0	0.0	0.0
Defined Benefit Plan, Interest Cost	0.1	0.2	0.3	0.5
Defined Benefit Plan, Expected Return on Plan Assets	0.0	0.0	0.0	0.0
Amortization of actuarial loss	0.0	0.0	0.1	0.1
Defined Benefit Plan Net Periodic Benefit Cost Before Portion Allocated To Affiliate	0.1	0.2	0.4	0.6
Defined Benefit Plan Net Periodic Benefit Cost Portion Allocated To Affiliate	0.0	0.0	0.0	0.0
Defined Benefit Plan, Net Periodic Benefit Cost	$ 0.1	$ 0.2	$ 0.4	$ 0.6