Note 11 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2014

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

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

	Year Ended December 31,
	2014		2013			2012
Risk-free interest rate		—		1.41	%		1.32	%
Expected life (in years)		—		6.25			6.22
Dividend yield		—		—			—
Expected volatility		—		50	%		50	%

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

	Number of Shares			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Life		Aggregate Intrinsic Value
Outstanding at December 31, 2013		3,883,097		$	9.26		6.33	$	16,229
Granted		—			—
Exercised		(788,196	)		5.45
Canceled		(89,307	)		12.52
Outstanding at December 31, 2014		3,005,594		$	10.16		6.12	$	25,302
Exercisable at December 31, 2014		2,349,476		$	9.69		5.82	$	20,880
Vested and expected to vest in the future as of December 31, 2014		3,001,391		$	10.16		6.12	$	25,273

Schedule of Nonvested Restricted Stock Units Activity [Table Text Block]

	Number of Shares			Weighted Average Grant Date Fair Value Per Share
Outstanding at December 31, 2013		3,209,567		$	11.69
Granted		2,878,836			13.99
Vested		(1,098,924	)		12.61
Canceled		(199,857	)		11.92
Outstanding at December 31, 2014		4,789,622		$	12.85
Expected to vest in the future as of December 31, 2014		4,712,501

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

	Year Ended December 31,
	2014			2013			2012
Risk-free interest rate		0.07	%		0.10	%		0.13	%
Expected life (in years)		0.50			0.49			0.50
Dividend yield		—			—			—
Expected volatility		40	%		45	%		81	%
Estimated fair value	$	3.55		$	2.86		$	4.69

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

	Year Ended December 31,
	2014		2013		2012
Cost of revenue	$	1,260	$	1,086	$	726
Research and development		12,420		8,586		5,833
Sales and marketing		4,079		3,204		2,660
General and administrative		4,701		4,102		3,240
	$	22,460	$	16,978	$	12,459