Basis of Presentation and Summary of Significant Accounting Policies New Accounting Standards (Details Textual) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Dec. 31, 2017	Dec. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ 574,966	$ 574,966	$ 426,932	$ 341,003
Receivables, net	219,072	219,072		190,426
Contract assets	8,305	8,305		3,964
Current portion of deferred revenue	(327,078)	(327,078)		(336,297)
Accounts payable and accrued liabilities	$ 243,158	$ 243,158		$ 221,101
Percentage of revenue mix recognizable over time	90.00%	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 | Initial application period cumulative effect adjustments
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Retained earnings	$ (83,068)	$ (83,068)	85,400
Receivables, net	(19,328)	(19,328)	47,300
Contract assets			4,000
Current portion of deferred revenue	(57,720)	(57,720)	(57,400)
Accounts payable and accrued liabilities	$ (26,920)	$ (26,920)	23,300
Deferred sales commission			$ 27,300