General (Details Textual) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operations commenced date			Jan. 01, 2005
Subsidiary or equity method investee, number	9		9
Entity incorporation, date of incorporation			Nov. 24, 2004
Revenue	$ 62,190	$ 49,431	$ 115,718	$ 89,024
Deferred revenues, noncurrent	71,663		71,663		$ 73,493
Deferred revenues, current	6,274		6,274		6,608
Contract with customer, liability, revenue recognized			48
Other than temporary impairment losses, investments, available-for-sale securities			$ 0
Short-term investments | US Treasury Securities | Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Short-term Investment, maturity period			1 year
Foreign Exchange Contract
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Derivative, gain on derivative, net, total	948	653	$ 900	918
Material ineffective hedges recognized			0	0
Accounting Standards Update 2014-09 | As of December 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reduction in accumulated deficit	$ 13,064		$ 13,064
Accounting Standards Update 2014-09 | Adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue		$ (743)		$ (1,530)	(1,974)
Deferred sales commission					13,486
Deferred revenues, noncurrent					(398)
Deferred revenues, current					(426)
Deferred tax liabilities					$ 1,246