Fair Value Measurements - Reconciliation of Beginning and Ending Balance of Level 3 Assets and Liabilities (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Fair Value, Asset and Liabilities Measured on Recurring and Nonrecurring Basis, Level 3 [Roll Forward]
Earnout payments	$ 4,557	$ 7,461
Fair Value, Inputs, Level 3 [Member] | Acquisition Earnout Accruals [Member]
Fair Value, Asset and Liabilities Measured on Recurring and Nonrecurring Basis, Level 3 [Roll Forward]
Beginning balance, acquisition earnout accruals	(10,991)
Earnout Accretion Fair Value Disclosure	(836)
Earnout Payments Fair Value Disclosure	4,557
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Business Combination, Acquisition Earnout Adjustment, Fair Value	705
Foreign currency translation	(415)
Ending balance, acquisition earnout accruals	$ (6,980)