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Amount of liability recognized arising from contingent consideration in a business combination.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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FAIR VALUE MEASUREMENTS (Details) - USD ($)	3 Months Ended		9 Months Ended
FAIR VALUE MEASUREMENTS (Details) - USD ($)	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Oct. 31, 2018	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	$ 50,219,000	$ 15,241,000	$ 38,837,000	$ 57,349,000
Change in fair value of contingent consideration	3,839,000	2,105,000	21,221,000	1,197,000
Contingent consideration additions	0	0	0	5,800,000
Contingent consideration payments	0	(1,000,000)	(6,000,000)	(48,000,000)
Ending balance	$ 54,058,000	$ 16,346,000	$ 54,058,000	$ 16,346,000
Minimum
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration					$ 0	$ 4,400,000	$ 3,000,000.0	$ 0
Maximum
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Contingent consideration					$ 70,200,000	$ 8,800,000	$ 6,000,000.0	$ 1,000,000.0