Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Assets:
Total assets measured at fair value	$ 133,370	$ 133,147
Liabilities:
Total liabilities measured at fair value	5,675	5,516
Money Market Funds [Member]
Assets:
Cash Equivalents, at Carrying Value	133,370	133,147
Contingent consideration [Member]
Liabilities:
Total liabilities measured at fair value	5,675	5,516
Level 1 [Member]
Assets:
Total assets measured at fair value	133,370	133,147
Liabilities:
Total liabilities measured at fair value	0	0
Level 1 [Member] | Money Market Funds [Member]
Assets:
Cash Equivalents, at Carrying Value	133,370	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] | Money Market Funds [Member]
Assets:
Cash Equivalents, at Carrying Value	0	0
Level 2 [Member] | Contingent consideration [Member]
Liabilities:
Total liabilities measured at fair value	0	0
Level 3 [Member]
Assets:
Unrealized gain on foreign currency translation	(1)
Total assets measured at fair value	0	0
Liabilities:
Total liabilities measured at fair value	5,675	5,516
Level 3 [Member] | Money Market Funds [Member]
Assets:
Cash Equivalents, at Carrying Value	0	0
Level 3 [Member] | Contingent consideration [Member]
Liabilities:
Total liabilities measured at fair value	$ 5,675	$ 5,516