Stock-Based Compensation (Stock-Based Compensation Expense) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	$ 53,154	$ 33,347	$ 33,951
Stock-based compensation expense	53,154	33,347	33,951
Related income tax benefits	(20,503)	(10,538)	(11,656)
Stock-based compensation expense, net of taxes	$ 32,651	$ 22,809	$ 22,295
Basic earnings per share	$ (0.38)	$ (0.26)	$ (0.25)
Diluted earnings per share	$ (0.38)	$ (0.26)	$ (0.24)
Software Licenses
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	$ 969	$ 701	$ 745
Maintenance And Service [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	2,533	1,578	1,868
Selling, General And Administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	30,817	15,990	17,153
Research And Development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense before taxes	$ 18,835	$ 15,078	$ 14,185