Basis of Presentation and Summary of Significant Accounting Policies New Accounting Standards (Details Textual) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Dec. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ 499,817	$ 426,932	$ 341,003
Receivables, net	225,822		190,426
Contract assets	6,077		3,964
Current portion of deferred revenue	310,639		336,297
Accounts payable and accrued liabilities	$ 210,784		$ 221,101
Percentage of revenue mix recognizable over time	90.00%
Accounting Standards Update 2016-16
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings		(8,349)
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings		91,640
Accounting Standards Update 2014-09 | Adjustments
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ (79,876)	85,400
Receivables, net	(18,538)	47,300
Contract assets		4,000
Current portion of deferred revenue	78,462	57,400
Accounts payable and accrued liabilities	$ (40,357)	23,300
Deferred sales commission		$ 27,300