BENEFIT PLANS - OTHER CHANGES IN PLAN ASSETS AND BENEFIT OBLIGATIONS RECOGNIZED IN AOCI (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Pension Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	$ (48.6)	$ 88.5	$ (23.4)
Net prior service cost (credit)	(0.3)	0.4	0.0
Amortization	(7.6)	(2.6)	(5.0)
Total recognized in AOCI	(56.5)	86.3	(28.4)
Total recognized in net periodic benefit cost and AOCI	(30.7)	108.7	(5.2)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss (gain)	(0.4)	1.4	(2.7)
Net prior service cost (credit)	0.0	0.0	0.0
Amortization	(0.2)	0.0	(0.3)
Total recognized in AOCI	(0.6)	1.4	(3.0)
Total recognized in net periodic benefit cost and AOCI	$ 0.6	$ 2.2	$ (2.0)