Note 3 - Stock Based Compensation (Tables)

9 Months Ended

Sep. 30, 2014

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

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan [Table Text Block]

	Three months ended September 30,				Nine months ended September 30,
	2014		2013		2014		2013
Stock options and employee stock purchase plan	$	1,380	$	1,326	$	4,555	$	5,156
Restricted stock awards		285		104		438		518
Total stock-based compensation expense	$	1,665	$	1,430	$	4,993	$	5,674

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

	Three months ended September 30,					Nine months ended September 30,
	2014			2013		2014			2013
Expected volatility		70	%		N/A		58	%		59	%
Expected life (in years)		4.0			N/A		4.2			4.0
Risk-free interest rate		2.16	%		N/A		1.88	%		0.74	%
Dividend yield		—	%		N/A		—	%		—	%
Fair value per stock option	$	18.34			N/A	$	12.54		$	6.77
Forfeiture rate		8	%		N/A		8	%		8	%

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

	Number of Options (in thousands)		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2013		9,228	$	4.45		1.61	$	186,169
Granted		1,295		26.92
Exercised		(3,481)		1.74
Forfeited		(43)		19.66
Outstanding at September 30, 2014		6,999	$	9.86		3.02	$	184,869
Exercisable at September 30, 2014		4,998	$	4.92		1.97	$	156,650

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

	Number of Shares (in thousands)		Weighted Average Grant Date Fair Value
Non-vested at December 31, 2013		16	$	15.36
Granted		337		27.54
Forfeited		—		—
Vested		(16)		15.36
Non-vested at September 30, 2014		337	$	27.54