Significant Accounting Policies (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2017	Dec. 31, 2015
Significant Accounting Policies [Line Items]
Short term restricted cash	$ 0	$ 0
Long term restricted cash included in other assets	0	547,000	$ 488,000
Asset impairment charges	0	0	0
Deferred revenue, revenue recognized	73,176,000
Sales returns	$ 0	0	$ 0
Granted (in shares)	0
Dividend yield			0.00%
Expected volatility rate			62.10%
Risk free interest rate			1.42%
Expected life			6 years 3 months
Stock-based compensation	$ 34,961,000	19,835,000	$ 12,938,000
Gain on derivative	98,000
Severance and retirement costs	$ 6,765,000	$ 4,801,000	3,775,000
Antidilutive securities excluded from computation of earnings per share, shares	3,173,188	3,505,729
Revenues	$ 270,288,000	$ 215,390,000	165,863,000
Deferred revenues	87,729,000	73,493,000
Deferred revenues	6,487,000	6,608,000
Deferred tax liabilities		134,000
Accumulated deficit	(137,968,000)	(109,390,000)
Other Noncurrent Liabilities
Significant Accounting Policies [Line Items]
Restructuring reserve	$ 2,391,000	1,781,000
Foreign Plan | VSUK Plan
Significant Accounting Policies [Line Items]
Defined contribution plan, maximum annual contributions per employee, percent	8.33%
United Kingdom | VSUK Plan
Significant Accounting Policies [Line Items]
Defined contribution plan, employer matching contribution, percent of match	100.00%
Defined contribution plan, employer matching contribution, percent of base pay	3.00%
Israel | VSIR Plan
Significant Accounting Policies [Line Items]
Defined contribution plan, employer matching contribution, percent of match	100.00%
Deferred Salary Arrangement | United States
Significant Accounting Policies [Line Items]
Defined contribution plan, employer matching contribution, percent of match	100.00%
Defined contribution, plan employer matching contribution, percent of participants contribution	50.00%
Foreign Exchange Contract
Significant Accounting Policies [Line Items]
Derivative, gain on derivative, net	$ 3,741,000	2,649,000
Derivative instruments, gain (loss) recognized in income, ineffective portion and amount excluded from effectiveness testing, net	0	0
Accounting Standards Update 2016-09
Significant Accounting Policies [Line Items]
Effect of adoption of ASU			0
Deferred tax assets, operating loss carryforwards, domestic		7,131,000
Deferred tax assets, operating loss carryforwards, state and local		718,000
Accumulated deficit				$ 1,302,000
Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Effect of adoption of ASU					$ (9,697,000)
Deferred revenues		73,493,000
Deferred revenues		6,608,000
Accumulated deficit		(109,390,000)
Accounting Standards Update 2014-09 | Restatement Adjustments | Year Ended December 31, 2017
Significant Accounting Policies [Line Items]
Revenues	1,974,000
Accounting Standards Update 2014-09 | Restatement Adjustments | Year Ended December 31, 2016
Significant Accounting Policies [Line Items]
Revenues		$ 1,407,000
Accounting Standards Update 2014-09 | Restatement Adjustments | As of January 1, 2016
Significant Accounting Policies [Line Items]
Deferred commission	13,486,000
Deferred revenues	398,000
Deferred revenues	426,000
Deferred tax liabilities	1,246,000
Accumulated deficit	$ 9,697,000
Accumulated deficit | Accounting Standards Update 2016-09
Significant Accounting Policies [Line Items]
Effect of adoption of ASU			$ 2,616,000
Accumulated deficit | Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Effect of adoption of ASU					$ (9,697,000)
Israel, New Shekels
Significant Accounting Policies [Line Items]
Investment interest rate		0.03%
Minimum | Israel | VSIR Plan
Significant Accounting Policies [Line Items]
Defined contribution, plan employer matching contribution, percent of participants contribution	3.00%
Defined contribution plan, employer matching contribution, percent of base pay	3.00%
Minimum | Deferred Salary Arrangement | United States
Significant Accounting Policies [Line Items]
Defined contribution plan, contributions, percentage of participants base pay	3.00%
Minimum | Accounting Standards Update 2016-02
Significant Accounting Policies [Line Items]
Operating lease, liability	$ 60,000,000
Operating lease, right-of-use asset	$ 60,000,000
Minimum | United States of America, Dollars
Significant Accounting Policies [Line Items]
Investment interest rate	0.60%	0.60%
Maximum | Israel | VSIR Plan
Significant Accounting Policies [Line Items]
Defined contribution, plan employer matching contribution, percent of participants contribution	50.00%
Defined contribution plan, employer matching contribution, percent of base pay	5.00%
Maximum | Deferred Salary Arrangement | United States
Significant Accounting Policies [Line Items]
Defined contribution plan, employer matching contribution, percent of base pay	3.00%
Defined contribution plan, contributions, percentage of participants base pay	5.00%
Participant matching contribution percentage of base remuneration	80.00%
Maximum | Accounting Standards Update 2016-02
Significant Accounting Policies [Line Items]
Operating lease, liability	$ 70,000,000
Operating lease, right-of-use asset	$ 70,000,000
Maximum | United States of America, Dollars
Significant Accounting Policies [Line Items]
Investment interest rate	2.77%	1.35%
Short-term Deposits | US Treasury Securities | Maximum
Significant Accounting Policies [Line Items]
Short term investment maturity period	1 year	1 year