Note 3 - Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2021

Notes Tables

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

	Three Months Ended June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Cost of revenue	$	885	$	642	$	1,700	$	1,199
Research and development		6,752		4,962		12,918		9,332
Selling, general and administrative		24,489		15,440		46,092		29,075
Total stock-based compensation expense	$	32,126	$	21,044	$	60,710	$	39,606
Tax benefit related to stock-based compensation (1)	$	381	$	468	$	811	$	938

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, 2021		161		$	151.62		1,390		$	132.60		1,554		$	40.40		3,105		$	87.42
Granted		40		$	373.24		365	(1)	$	352.09		-		$	-		405		$	354.19
Vested		(47	)	$	138.82		(431	)	$	91.95		(162	)	$	23.57		(640	)	$	78.14
Forfeited		(6	)	$	190.54		(10	)	$	91.39		(3	)	$	68.48		(19	)	$	117.01
Outstanding at June 30, 2021		148		$	214.40		1,314		$	207.33		1,389		$	42.30		2,851		$	127.26

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

	Six Months Ended June 30,
	2021			2020
Expected term (in years)		0.5			0.5
Expected volatility		43.3	%		31.4	%
Risk-free interest rate		0.1	%		1.6	%
Dividend yield		0.6	%		1.1	%