Note 3 - Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2020

Notes Tables

Share-based Payment Arrangement, Cost by Plan [Table Text Block]

	Three Months Ended March 31,
	2020		2019
Cost of revenue	$	557	$	531
Research and development		4,370		4,429
Selling, general and administrative		13,635		11,050
Total stock-based compensation expense	$	18,562	$	16,010
Tax benefit related to stock-based compensation (1)	$	470	$	838

Share-based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity [Table Text Block]

	Time-Based RSUs					PSUs and MPSUs					MSUs					Total
	Number of Shares			Weighted-Average Grant Date Fair Value Per Share		Number of Shares			Weighted-Average Grant Date Fair Value Per Share		Number of Shares			Weighted-Average Grant Date Fair Value Per Share		Number of Shares			Weighted-Average Grant Date Fair Value Per Share
Outstanding at January 1, 2020		180		$	115.45		1,987		$	74.50		1,886		$	37.63		4,053		$	59.16
Granted		47		$	183.53		324	(1)	$	168.69		-		$	-		371		$	170.56
Vested		(24	)	$	104.06		(979	)	$	56.22		(81	)	$	23.57		(1,084	)	$	54.85
Forfeited		(2	)	$	114.71		(7	)	$	81.64		(3	)	$	68.48		(12	)	$	83.20
Outstanding at March 31, 2020		201		$	132.71		1,325		$	110.99		1,802		$	38.21		3,328		$	72.88

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

	Three Months Ended March 31,
	2020			2019
Expected term (in years)		0.5			0.5
Expected volatility		31.4	%		37.3	%
Risk-free interest rate		1.6	%		2.5	%
Dividend yield		1.1	%		1.2	%