FAIR VALUE MEASUREMENTS (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Sep. 19, 2017	Jun. 14, 2017	May 31, 2017	Nov. 16, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Annual interest rate on convertible senior notes					0.625%
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at December 31, 2017	$ 57,349,000	$ 23,100,000
Change in fair value of contingent consideration	(741,000)	8,746,000
Contingent consideration additions	0	0
Contingent consideration payments	(23,500,000)	0
Balance at March 31, 2018	$ 33,108,000	$ 31,846,000
Minimum
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration			$ 0	$ 1,000,000
Maximum
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration			$ 9,000,000	$ 7,000,000		$ 22,500,000