Segment and Geographic Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Revenues from External Customers and Long-Lived Assets [Line Items]
Number of operating segments | segment									1
Total Revenue	$ 307,216	$ 308,616	$ 255,993	$ 263,852	$ 278,312	$ 278,315	$ 272,796	$ 273,501	$ 1,135,677	$ 1,102,924	$ 1,143,371
Property and Equipment, net	53,229				37,670				53,229	37,670
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenue									1,005,948	1,069,567	1,116,136
Property and Equipment, net	42,666				37,328				42,666	37,328
Non-U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Revenue									129,729	33,357	$ 27,235
Property and Equipment, net	$ 10,563				$ 342				$ 10,563	$ 342