Fair Value Measurements - Fair Value Hierarchy of Financial Assets Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value, Inputs, Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Acquisition contingent consideration obligations	$ (1,200)
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents (money market accounts)	69,789	$ 77,935
Acquisition contingent consideration obligations	(1,799)	(3,088)
Fair value assets and liabilities measured on recurring basis, total	67,990	74,847
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents (money market accounts)	69,789	77,935
Acquisition contingent consideration obligations	0	0
Fair value assets and liabilities measured on recurring basis, total	69,789	77,935
Fair Value, Measurements, Recurring | 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, Measurements, Recurring | 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	(1,799)	(3,088)
Fair value assets and liabilities measured on recurring basis, total	$ (1,799)	$ (3,088)