Note 3 - Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2020

Notes Tables

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2020		2019		2020		2019
Cost of revenue	$	642	$	663	$	1,199	$	1,193
Research and development		4,962		5,412		9,332		9,841
Selling, general and administrative		15,440		16,634		29,075		27,685
Total stock-based compensation expense	$	21,044	$	22,709	$	39,606	$	38,719
Tax benefit related to stock-based compensation (1)	$	468	$	706	$	938	$	1,544

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		70		$	181.41		383	(1)	$	169.65		-		$	-		453		$	171.47
Vested		(60	)	$	105.95		(1,058	)	$	57.29		(162	)	$	23.57		(1,280	)	$	55.30
Forfeited		(4	)	$	129.31		(9	)	$	83.15		(5	)	$	68.48		(18	)	$	89.81
Outstanding at June 30, 2020		186		$	143.09		1,303		$	116.39		1,719		$	38.86		3,208		$	76.39

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

	Six Months Ended June 30,
	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	%