Segment, Geographic and Product Information - Geographic Information Regarding Revenues (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Total revenues	$ 521,137	$ 455,642	$ 1,617,075	$ 1,471,459
United States [Member]
Revenues:
Total revenues	134,230	126,534	426,221	411,648
United Kingdom [Member]
Revenues:
Total revenues	212,121	193,622	666,374	621,299
Asia [Member]
Revenues:
Total revenues	84,730	70,602	258,594	208,874
Other Europe/MEA [Member]
Revenues:
Total revenues	53,374	36,163	157,566	129,796
France [Member]
Revenues:
Total revenues	21,724	15,800	64,343	58,170
Other Americas [Member]
Revenues:
Total revenues	$ 14,958	$ 12,921	$ 43,977	$ 41,672