Revenue - Changes in Deferred Revenue (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Deferred Revenue Disclosure [Abstract]
Deferred revenue, beginning balance	$ 145,344
Deferral of revenue	215,188
Recognition of deferred revenue	(200,061)
Foreign currency translation	(4,336)
Deferred revenue, ending balance	$ 156,135