FAIR VALUE MEASUREMENTS - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Liabilities:
Highly liquid investments, maturity period (in months)	3 months
Recurring basis
Assets:
Cash equivalents	$ 296.6	$ 167.2
Liabilities:
Acquisition-related contingent consideration	(985.3)	(1,155.9)
Recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash equivalents	208.5	156.1
Liabilities:
Acquisition-related contingent consideration	0.0	0.0
Recurring basis | Significant Other Observable Inputs (Level 2)
Assets:
Cash equivalents	88.1	11.1
Liabilities:
Acquisition-related contingent consideration	0.0	0.0
Recurring basis | Significant Unobservable Inputs (Level 3)
Assets:
Cash equivalents	0.0	0.0
Liabilities:
Acquisition-related contingent consideration	$ (985.3)	$ (1,155.9)