Note 7 - Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2016

Notes Tables

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

	Year Ended December 31,
	2016		2015		2014
Cost of revenue	$	1,575	$	1,166	$	903
Research and development		14,041		11,156		9,019
Selling, general and administrative		29,373		29,241		23,532
Total	$	44,989	$	41,563	$	33,454

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, 2014		754		$	19.41		1,028			$	23.02		1,800		$	23.57		3,582		$	22.53
Granted		335		$	36.71		952		(1)	$	34.65		-		$	-		1,287		$	35.19
Released		(468	)	$	20.36		(304	)		$	18.12		-		$	-		(772	)	$	19.48
Forfeited		(32	)	$	19.75		(17	)		$	19.79		-		$	-		(49	)	$	19.77
Outstanding at December 31, 2014		589		$	28.48		1,659			$	28.11		1,800		$	23.57		4,048		$	26.14
Granted		271		$	49.82		927		(1)	$	47.61		-		$	-		1,198		$	48.11
Released		(319	)	$	26.56		(629	)		$	23.40		-		$	-		(948	)	$	24.47
Forfeited		(42	)	$	35.60		(24	)		$	28.68		-		$	-		(66	)	$	33.06
Outstanding at December 31, 2015		499		$	40.75		1,933			$	38.99		1,800		$	23.57		4,232		$	32.64
Granted		133		$	63.00		1,216		(1)	$	41.12		-		$	-		1,349		$	43.28
Released		(239	)	$	36.43		(736	)		$	29.71		-		$	-		(975	)	$	31.36
Forfeited		(27	)	$	45.35		(129	)		$	36.82		(180	)	$	23.57		(336	)	$	30.38
Outstanding at December 31, 2016		366		$	51.35		2,284			$	43.24		1,620		$	23.57		4,270		$	36.47

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

	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value
	(in thousands)					(in years)		(in thousands)
Outstanding at January 1, 2014		1,356		$	15.86		1.9	$	25,506
Exercised		(742	)	$	16.09
Forfeited and expired		(24	)	$	10.07
Outstanding at December 31, 2014		590		$	15.80		1.2	$	20,039
Exercised		(498	)	$	15.55
Forfeited and expired		(2	)	$	6.10
Outstanding at December 31, 2015		90		$	17.50		1.3	$	4,134
Exercised		(76	)	$	17.80
Outstanding at December 31, 2016		14		$	15.88		1.0	$	921
Options exercisable at December 31, 2016 and expected to vest		14		$	15.88		1.0	$	921
Options exercisable at December 31, 2016		14		$	15.88		1.0	$	921

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

	Year Ended December 31,
	2016			2015			2014
Expected term (years)		0.5			0.5			0.5
Expected volatility		28.6	%		30.3	%		29.4	%
Risk-free interest rate		0.4	%		0.2	%		0.1	%
Dividend yield		1.2	%		1.4	%		0.7	%