FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Liabilities:
Contingent consideration	$ 103,200	$ 120,020
Significant Unobservable Inputs (Level 3)
Liabilities:
Contingent consideration	103,200	120,020
Carrying Amount
Assets:
Money market funds (cash equivalents)	16,370	31,146
Liabilities:
Contingent consideration	103,200	120,020
Fair Value | Recurring
Assets:
Money market funds (cash equivalents)	16,370	31,146
Liabilities:
Contingent consideration	103,200	120,020
Fair Value | Recurring | Quoted Prices in Active Markets (Level 1)
Assets:
Money market funds (cash equivalents)	16,370	31,146
Liabilities:
Contingent consideration	0	0
Fair Value | Recurring | Significant other Observable Inputs (Level 2)
Assets:
Money market funds (cash equivalents)	0	0
Liabilities:
Contingent consideration	0	0
Fair Value | Recurring | Significant Unobservable Inputs (Level 3)
Assets:
Money market funds (cash equivalents)	0	0
Liabilities:
Contingent consideration	$ 103,200	$ 120,020