Fair Value Measurement - Reconciliation of the Beginning and Ending Level 3 Net Liabilities (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payment of contingent earnout consideration		$ (5,189)	$ (2,214)
Adjustment to estimated fair value of contingent earnout consideration (included within Selling, general and administrative expense)	$ 856	252	928
Accretion of contingent earnout consideration (included within other expense, net)		(295)	$ (1,730)
Significant Unobservable Inputs (Level 3) [Member] | Zero2Ten and Branchbird Contingent Earnout Consideration [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance		8,089
Payment of contingent earnout consideration		(8,132)
Adjustment to estimated fair value of contingent earnout consideration (included within Selling, general and administrative expense)		(252)
Accretion of contingent earnout consideration (included within other expense, net)		$ 295
Ending balance