Segment Information - Revenue Classified by Major Geographic Areas (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 244,679	$ 243,376	$ 749,536	$ 726,352
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	233,846	231,777	710,198	693,251
Europe/Middle East [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	9,106	9,210	32,983	26,930
Asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	1,256	1,309	5,024	2,843
South America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 471	$ 1,080	$ 1,331	$ 3,328