Note 2 - Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2017

Notes Tables

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
Cost of revenue	$	452	$	380	$	810	$	814
Research and development		3,961		3,318		7,459		7,016
Selling, general and administrative		10,714		8,049		18,520		12,896
Total	$	15,127	$	11,747	$	26,789	$	20,726

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

	Time-Based RSUs			Weighted-Average Grant Date Fair Value Per Share		PSUs and MPSUs			Weighted-Average Grant Date Fair Value Per Share		MSUs		Weighted-Average Grant Date Fair Value Per Share		Total			Weighted-Average Grant Date Fair Value Per Share
Outstanding at January 1, 2017		366		$	51.35		2,284		$	43.24		1,620	$	23.57		4,270		$	36.47
Granted		69		$	91.57		645	(1)	$	61.08		-	$	-		714		$	64.02
Released		(103	)	$	46.84		(440	)	$	42.87		-	$	-		(543	)	$	43.63
Forfeited		(10	)	$	61.12		(6	)	$	49.82		-	$	-		(16	)	$	57.05
Outstanding at June 30, 2017		322		$	61.12		2,483		$	47.92		1,620	$	23.57		4,425		$	39.96

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

	Six Months Ended June 30,
	2017			2016
Expected term (years)		0.5			0.5
Expected volatility		23.4	%		29.7	%
Risk-free interest rate		0.7	%		0.4	%
Dividend yield		0.9	%		1.4	%