Operating Segments and Related Information (Details 4) - 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
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue	$ 437,647	$ 381,928	$ 392,975	$ 344,517	$ 434,366	$ 375,366	$ 369,380	$ 351,542	$ 1,557,067	$ 1,530,654	$ 1,496,372
United States
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									822,892	783,685	755,640
Europe [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									339,544	350,118	370,800
Mid_East/Africa [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									125,760	138,186	59,917
Canada/Latin_America [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									83,825	94,032	155,904
Asia [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Revenue									$ 185,046	$ 164,633	$ 154,111