Revenue Recognition (Disaggregation of Revenue by Principal Geographic Area, Based on Customers' Domiciles) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 580,752	$ 508,940	$ 1,118,408	$ 970,961
United States
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	356,736	315,695	684,197	604,308
Europe, the Middle East and Africa
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	122,270	102,482	242,844	198,910
Asia Pacific Region
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	62,505	56,085	118,544	105,037
Canada
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	26,407	23,078	48,951	41,826
Latin America
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	$ 12,834	$ 11,600	$ 23,872	$ 20,880