Operating Segments and Related Information (Details 5) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 405,228	$ 381,928	$ 1,187,429	$ 1,119,420
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	229,400	216,200	647,900	587,600
Canada/Latin_America
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	19,401	23,825	66,727	60,224
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	71,949	66,207	240,656	255,331
Mid_East/Africa
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	41,889	37,253	98,231	89,830
Asia
Revenues from External Customers and Long-Lived Assets [Line Items]
Revenue	$ 42,639	$ 38,406	$ 133,877	$ 126,398