Fair Value Measurement - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets:
Total assets measured at fair value	$ 133,540
Liabilities:
Total liabilities measured at fair value	5,175	$ 5,516
Cash equivalents [Member]
Assets:
Total assets measured at fair value	133,540	133,147
Contingent consideration [Member]
Liabilities:
Total liabilities measured at fair value		5,516
Level 1 [Member]
Assets:
Total assets measured at fair value		133,147
Liabilities:
Total liabilities measured at fair value	0	0
Level 1 [Member] | Cash equivalents [Member]
Assets:
Total assets measured at fair value	133,540	133,147
Level 1 [Member] | Contingent consideration [Member]
Liabilities:
Total liabilities measured at fair value	0	0
Level 2 [Member]
Assets:
Total assets measured at fair value	0	0
Liabilities:
Total liabilities measured at fair value	0	0
Level 2 [Member] | Cash equivalents [Member]
Assets:
Total assets measured at fair value	0	0
Level 2 [Member] | Contingent consideration [Member]
Liabilities:
Total liabilities measured at fair value	0	0
Level 3 [Member]
Assets:
Total assets measured at fair value	0	0
Liabilities:
Total liabilities measured at fair value	5,175	5,516
Level 3 [Member] | Cash equivalents [Member]
Assets:
Total assets measured at fair value	0	0
Level 3 [Member] | Contingent consideration [Member]
Liabilities:
Total liabilities measured at fair value	$ 5,175	$ 5,516