Revenues, Recognition and Allowances (Details 1) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	[1]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 13,415		$ 18,143
Accrued expenses	11,138		$ 13,502
Revenue, net	14,545	$ 19,891
Cost of revenues	9,325	$ 8,957
Calculated under Revenue Guidance in Effect before Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	16,684
Accrued expenses	14,407
Revenue, net	15,180
Cost of revenues	9,960
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	(3,269)
Accrued expenses	(3,269)
Revenue, net	(635)
Cost of revenues	$ (635)

[1] Derived from the audited December 31, 2017 financial statements