Segment Information - Financial Information by Major Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenue:
Total revenue	$ 251,671	$ 255,946	$ 317,035	$ 264,396	$ 223,155	$ 299,802	$ 256,391	$ 285,641	$ 1,089,048	$ 1,064,987	$ 953,347
Long-lived assets:
Total long-lived assets	228,442				222,809				228,442	222,809	225,356
United States
Revenue:
Total revenue									726,436	718,538	637,482
Long-lived assets:
Total long-lived assets	141,051				130,401				141,051	130,401	132,315
EMEA
Revenue:
Total revenue									220,046	192,674	166,931
Long-lived assets:
Total long-lived assets	15,714				14,215				15,714	14,215	10,055
Canada
Revenue:
Total revenue									142,566	153,775	148,934
Long-lived assets:
Total long-lived assets	$ 71,677				$ 78,193				$ 71,677	$ 78,193	$ 82,986