Note 4 - Stockholder's Equity (Deficiency) (Tables)

3 Months Ended

Mar. 31, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Share-based Compensation, Stock Options, Activity [Table Text Block]

	Period ended March 31, 2015 (unaudited)
	Number			Average exercise price		Aggregate intrinsic value (in thousands)		Average remaining contractual life (years)
Options outstanding at the beginning of the year		4,080,611		$	9.697	$	95,855		6.092
Granted		161,200		$	29.880
Exercised		(140,716	)	$	3.728
Forfeited		(58,995	)	$	28.659
Options outstanding at the end of the period		4,042,100		$	10.433	$	64,869		6.049
Vested and expected to vest		3,932,028		$	10.064	$	64,408		5.961
Options exercisable at the end of the period		2,578,803		$	3.488	$	57,852		4.326

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]

Range of exercise price	Options outstanding as of March 31, 2015		Weighted average remaining contractual life (years)		Weighted average exercise price		Options exercisable as of March 31, 2015		Weighted average remaining contractual life (years)		Weighted average exercise price of options exercisable
$0.070-0.901		517,811		2.483	$	0.812		517,811		2.483	$	0.812
$1.039-1.576		1,635,172		4.021	$	1.263		1,635,172		4.021	$	1.263
$6.230-8.800		154,818		6.645	$	6.754		126,326		6.568	$	6.761
$12.470		387,601		7.927	$	12.470		185,324		7.902	$	12.470
$21.000-24.230		1,004,548		9.233	$	21.609		66,556		8.625	$	21.756
$29.880		154,200		9.901	$	29.880		-		-		-
$39.860		187,950		8.981	$	39.860		47,614		8.981	$	39.860
		4,042,100		6.049	$	10.433		2,578,803		4.326	$	3.488

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]

	Period ended March 31, 2015
	unaudited
Expected dividend yield		0	%
Expected volatility		65	%
Risk-free interest rate		1.94	%
Expected term (years)		6.25

Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block]

	Options for shares of common stock		Exercise price per share		Options exercisable		Exercisable through
	(number)				(number)
February 2013		3,500	$	12.470		1,582	February 2023
August 2013		5,000	$	21.140		1,975	August 2023
October 2013		1,084	$	24.230		276	October 2023
March 2014		16,450	$	39.860		4,115	March 2024
May 2014		8,700	$	22.010		-	May 2024
August 2014		36,250	$	21.000		-	August 2024
November 2014		12,000	$	21.660		-	November 2024
		82,984				7,948

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	Three Months Ended March 31,
	2015		2014
	(unaudited)
	(in thousands)
Cost of revenues	$	91	$	20
Research and development		467		199
Sales and marketing		737		340
General and administrative		390		87
Total	$	1,685	$	646

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]

	Number of shares underlying outstanding restricted stock units			Weighted- average grant date fair value
Unvested balance - January 1, 2015		27,470		$	21.00
Granted		252,150		$	29.88
Vested		(2,478	)	$	21.00
Forfeited		(6,140	)	$	22.45
Unvested balance - March 31, 2015		271,002		$	29.23
Expected to vest – March 31, 2015		249,139