Segment Information - Revenue Classified by Major Geographic Areas (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 245,561	$ 255,168
United States [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	233,031	240,328
United Kingdom Israel [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	10,972	13,837
CHINA
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 1,558	$ 1,003