Operating Segments and Related Information (Details 4) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 474,738	$ 405,228	$ 402,729	$ 379,472	$ 437,647	$ 381,928	$ 392,975	$ 344,517	$ 1,662,167	$ 1,557,067	$ 1,530,654
United States
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									903,582	830,485	783,685
Europe [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									338,805	338,886	350,118
Asia [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									195,913	175,616	164,633
Mid_East/Africa [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									130,890	125,848	138,186
Canada/Latin_America [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									$ 92,977	$ 86,232	$ 94,032