FAIR VALUE MEASUREMENTS (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 11, 2018	Sep. 19, 2017	Jun. 14, 2017	May 31, 2017
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]
Beginning balance	$ 33,108,000	$ 31,846,000	$ 57,349,000	$ 23,100,000
Change in fair value of contingent consideration	(167,000)	9,393,000	(908,000)	18,139,000
Contingent consideration additions	5,800,000	4,988,000	5,800,000	4,988,000
Contingent consideration payments	(23,500,000)		(47,000,000)
Ending balance	$ 15,241,000	$ 46,227,000	$ 15,241,000	$ 46,227,000
Minimum
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration					$ 0	$ 0	$ 1,000,000
Maximum
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration					$ 8,750,000	$ 9,000,000	$ 6,000,000