General (Details Textual)			3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($) subsidiary	Dec. 31, 2017 USD ($)	Sep. 30, 2018 USD ($) subsidiary	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) subsidiary	Sep. 30, 2017 USD ($)	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 | subsidiary	9		9		9
Entity incorporation, date of incorporation					Nov. 24, 2004
Revenue			$ 67,052,000	$ 53,365,000	$ 182,770,000	$ 142,389,000
Deferred revenues, noncurrent	$ 72,544,000	$ 73,493,000	72,544,000		72,544,000		$ 73,493,000
Deferred revenues, current	$ 6,374,000	$ 6,608,000	6,374,000		6,374,000		6,608,000
Contract with customer, liability, revenue recognized					62,687,000
Other than temporary impairment losses, investments, available-for-sale securities			0		0
Loss in financial income, net			199,000	0	199,000	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	1 year
Foreign Exchange Contract
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Derivative, gain on derivative, net, total			1,194,000	774,000	2,094,000	1,692,000
Material ineffective hedges recognized			0	0	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	$ 13,064,000		$ 13,064,000		$ 13,064,000
Accounting Standards Update 2014-09 | Adjustments
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenue				$ (236,000)		$ (1,766,000)	(1,974,000)
Deferred sales commission		$ 13,486,000					13,486,000
Deferred revenues, noncurrent		(398,000)					(398,000)
Deferred revenues, current		(426,000)					(426,000)
Deferred tax liabilities		$ 1,246,000					$ 1,246,000