FAIR VALUE MEASUREMENT AND FINANCIAL INSTRUMENTS - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Liabilities:
Contingent consideration, net of current portion	$ 99,855	$ 120,020
Carrying Amount
Assets:
Money market funds (cash equivalents)	16,374	31,146
Liabilities:
Contingent consideration	8,985	0
Fair Value \| Recurring
Assets:
Money market funds (cash equivalents)	16,374	31,146
Liabilities:
Contingent consideration, net of current portion	99,855	120,020
Contingent consideration	8,985	0
Fair Value \| Recurring \| Quoted Prices in Active Markets (Level 1)
Assets:
Money market funds (cash equivalents)	16,374	31,146
Liabilities:
Contingent consideration, net of current portion	0	0
Contingent consideration	0	0
Fair Value \| Recurring \| Significant other Observable Inputs (Level 2)
Assets:
Money market funds (cash equivalents)	0	0
Liabilities:
Contingent consideration, net of current portion	0	0
Contingent consideration	0	0
Fair Value \| Recurring \| Significant Unobservable Inputs (Level 3)
Assets:
Money market funds (cash equivalents)	0	0
Liabilities:
Contingent consideration, net of current portion	99,855	120,020
Contingent consideration	$ 8,985	$ 0

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Amount of liability recognized arising from contingent consideration in a business combination, expected to be settled within one year or the normal operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 35
-Paragraph 1
-Subparagraph b
-URI http://asc.fasb.org/extlink&oid=116859824&loc=d3e6819-128478

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Amount of liability recognized arising from contingent consideration in a business combination, expected to be settled beyond one year or the normal operating cycle, if longer.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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