Fair Value Measurements - Fair Value Hierarchy of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - Fair value, measurements, recurring - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents (money market accounts)	$ 89,220	$ 65,010
Acquisition contingent consideration obligations	(8,752)	(1,968)
Fair value assets and liabilities measured on recurring basis, total	80,468	63,042
Fair value, inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents (money market accounts)	89,220	65,010
Acquisition contingent consideration obligations	0	0
Fair value assets and liabilities measured on recurring basis, total	89,220	65,010
Fair value, inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents (money market accounts)	0	0
Acquisition contingent consideration obligations	0	0
Fair value assets and liabilities measured on recurring basis, total	0	0
Fair value, inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents (money market accounts)	0	0
Acquisition contingent consideration obligations	(8,752)	(1,968)
Fair value assets and liabilities measured on recurring basis, total	$ (8,752)	$ (1,968)