FAIR VALUE MEASUREMENTS - Summary of changes in the fair value of the company's Level 3 financial liabilities (Details) $ in Millions	6 Months Ended
	Jun. 30, 2018 USD ($)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period	$ 56.6
Realized (gains) losses during period	2.2
Settlements	(56.6)
Balance at the end of the period	2.2
Contingent consideration liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period	56.6
Realized (gains) losses during period	2.2
Settlements	(56.6)
Balance at the end of the period	$ 2.2