Note 10 - Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2020

Notes Tables

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

	2020			2019			2018
Dividend yield		1.02	%		0.96	%		1.20	%
Volatility		47.3	%		42.8	%		41.3	%
Risk-free interest rate		0.3	%		1.7	%		2.7	%
Weighted average expected option term (in years)		4.9			4.7			4.8
Weighted average fair value per share of options granted	$	13.24		$	12.51		$	8.28

Share-based Payment Arrangement, Option, Activity [Table Text Block]

				Weighted		Weighted Average	Aggregate
	Number			Average		Remaining	Intrinsic
	of Shares			Exercise Price		Contractual Term	Value
						(in years)
Balance outstanding at December 31, 2019 (1)		1,047,094		$	23.19	4.31	$	13,366,595
Granted		222,110		$	36.67
Exercised (2)		(331,958	)	$	17.99		$	5,413,197
Canceled / Expired		(5,406	)	$	27.49
Balance outstanding at December 31, 2020 (3)		931,840		$	28.22	4.49	$	11,442,240
Vested and exercisable at December 31, 2020 (4)		274,411		$	23.08	3.50	$	4,780,656
Expected to vest at December 31, 2020		657,429		$	30.37	4.93
Total		931,840

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

				Weighted
				Average
				Grant Date
	Shares			Fair Value
Balance outstanding at December 31, 2019		188,681		$	26.14
Granted		46,146		$	36.86
Vested (1)		(50,669	)	$	22.76
Canceled		(37,143	)	$	27.88
Balance outstanding at December 31, 2020		147,015		$	30.24

Accelerated Share Repurchases [Table Text Block]

	2020		2019
Shares of common stock repurchased		16,537		20,524
Average per share repurchase price	$	34.47	$	33.28
Aggregage purchase price (in thousands)	$	570	$	683

Share-based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]

	2020		2019		2018
			(in thousands)
Stock option awards	$	1,938	$	1,580	$	1,457
Restricted stock units		1,084		1,062		892
Total stock-based compensation	$	3,022	$	2,642	$	2,349

	2020		2019		2018
			(in thousands)
Cost of sales	$	333	$	310	$	272
Sales and marketing		516		544		529
General and administrative		1,883		1,509		1,293
Research and development		290		279		255
Total stock-based compensation	$	3,022	$	2,642	$	2,349

Schedule of Dividends Payable [Table Text Block]

Record Date	Payment Date	Per Share Amount		Dividend Payment
				(in thousands)
Fiscal Year 2020
March 3, 2020	March 19, 2020	$	0.095	$	1,917
May 20, 2020	June 4, 2020	$	0.095	$	1,917
August 27, 2020	September 10, 2020	$	0.095	$	1,925
November 19, 2020	December 3, 2020	$	0.095	$	1,936
Fiscal Year 2019
March 22, 2019	April 5, 2019	$	0.085	$	1,672
May 22, 2019	June 6, 2019	$	0.085	$	1,672
August 21, 2019	September 5, 2019	$	0.085	$	1,691
November 20, 2019	December 5, 2019	$	0.085	$	1,701