Segment Information - Revenue Classified by Major Geographic Areas (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 254,928	$ 244,679	$ 249,689	$ 255,168	$ 293,362	$ 243,376	$ 243,830	$ 239,146	$ 1,004,464	$ 1,019,714	$ 952,612
Americas
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									955,361	978,249	916,568
Europe/Middle East
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									43,087	36,516	34,913
Asia
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									$ 6,016	$ 4,949	$ 1,131