FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS - Summary of Changes in Fair Value of Contingent Consideration (Details) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Beginning balance	$ 103,200	$ 84,800	$ 66,320
Change in fair value included in loss	5,640	18,400	18,480	$ (53,700)	$ (11,800)
Ending balance	$ 108,840	$ 103,200	$ 84,800	$ 66,320	$ 108,840
Contingent consideration liability, measurement input	0.084	0.118	0.145	0.179	0.084	0.118
Discount Rate | Minimum
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Contingent consideration liability, measurement input	0.084				0.084	0.056
Discount Rate | Maximum
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Contingent consideration liability, measurement input	0.088				0.088	0.118