Segment and Geographic Information - Geographic Information Regarding Revenues (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenues:
Total revenues	$ 651,960	$ 669,131	$ 1,290,996	$ 1,216,698
United States [Member]
Revenues:
Total revenues	373,835	378,145	728,909	685,085
United Kingdom [Member]
Revenues:
Total revenues	161,444	172,070	325,271	313,774
Asia [Member]
Revenues:
Total revenues	52,704	58,689	109,455	107,307
France [Member]
Revenues:
Total revenues	25,271	22,697	50,838	43,524
Other Americas [Member]
Revenues:
Total revenues	14,756	14,295	29,363	26,729
Other Europe/MEA [Member]
Revenues:
Total revenues	$ 23,950	$ 23,235	$ 47,160	$ 40,279