BENEFIT PLANS (Components of Net Periodic Benefit Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension Benefits
Weighted-average assumptions used to determine net periodic benefit cost at December 31,
Service cost	$ 3.6	$ 4.2	$ 4.5
Interest cost	31.3	30.4	31.1
Expected return on plan assets	(37.6)	(39.6)	(39.7)
Amortization of prior service cost	0.8	0.9	0.8
Recognized actuarial loss (gain)	13.6	15.8	12.9
Total net periodic benefit cost (income)	11.7	11.7	9.6
Other Benefits
Weighted-average assumptions used to determine net periodic benefit cost at December 31,
Service cost	0.3	0.3	0.3
Interest cost	0.8	0.7	0.8
Expected return on plan assets	(1.4)	(1.5)	(1.6)
Amortization of prior service cost	(1.1)	(1.2)	0.6
Recognized actuarial loss (gain)	0.8	0.6	(1.2)
Total net periodic benefit cost (income)	$ (0.6)	$ (1.1)	$ (1.1)