Note 10 - Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2021

Notes Tables

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

	2021			2020			2019
Dividend yield		0.91	%		1.02	%		0.96	%
Volatility		46.0	%		47.3	%		42.8	%
Risk-free interest rate		1.1	%		0.3	%		1.7	%
Weighted average expected option term (in years)		4.6			4.9			4.7
Weighted average fair value per share of options granted	$	17.64		$	13.24		$	12.51

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)		(in thousands)
Balance outstanding at December 31, 2018		1,462,575		$	16.41		4.54	$	12,214
Granted		195,379		$	35.53
Exercised		(509,693	)	$	9.53			$	11,488
Canceled / Expired		(101,167	)	$	17.90
Balance outstanding at December 31, 2019		1,047,094		$	28.22		4.31	$	13,367
Granted		222,110		$	36.67
Exercised		(331,958	)	$	17.99			$	5,413
Canceled / Expired		(5,406	)	$	27.49
Balance outstanding at December 31, 2020		931,840		$	28.22		4.49	$	11,442
Granted		151,161		$	48.60
Exercised		(217,121	)	$	20.95			$	6,975
Canceled / Expired		(19,126	)	$	23.18
Balance outstanding at December 31, 2021		846,754		$	33.83		4.50	$	13,888
Exercisable at:
December 31, 2019		309,501		$	19.64		3.50	$	5,047
December 31, 2020		274,411		$	23.08		3.50	$	4,781
December 31, 2021		301,692		$	27.40		3.30	$	6,886
Expected to vest at:
December 31, 2019		737,593		$	24.68		4.65
December 31, 2020		657,429		$	30.37		4.93
December 31, 2021		545,062		$	37.38		5.16

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

				Weighted
				Average
	Number			Grant Date
	of Shares			Fair Value
Balance outstanding at December 31, 2018		217,895		$	21.21
Granted		56,567		$	35.41
Vested		(61,058	)	$	18.46
Canceled		(24,723	)	$	22.19
Balance outstanding at December 31, 2019		188,681		$	26.14
Granted		46,146		$	36.86
Vested		(50,669	)	$	22.76
Canceled		(37,143	)	$	27.88
Balance outstanding at December 31, 2020		147,015		$	30.24
Granted		48,298		$	48.65
Vested		(51,414	)	$	26.32
Canceled		(10,068	)	$	30.70
Balance outstanding at December 31, 2021		133,831		$	38.26

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

			Weighted
			Average
	Number		Grant Date
	of Shares		Fair Value
Balance outstanding at December 31, 2020		-	$	-
Granted		31,181	$	48.60
Vested		-	$	-
Canceled		-	$	-
Balance outstanding at December 31, 2021		31,181	$	48.60

Accelerated Share Repurchases [Table Text Block]

	2021		2020		2019
Shares of common stock repurchased for net settlement of equity awards		16,333		16,537		20,524
Average per share repurchase price	$	49.10	$	34.47	$	33.28
Aggregage purchase price (in thousands)	$	802	$	570	$	683

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

	2021		2020		2019
	(in thousands)
Stock option awards	$	2,199	$	1,938	$	1,580
Restricted stock units		1,247		1,084		1,062
Performance-based restricted stock units		33		-		-
Total stock-based compensation	$	3,479	$	3,022	$	2,642

	2021		2020		2019
	(in thousands)
Cost of sales	$	407	$	333	$	310
Sales and marketing		527		516		544
General and administrative		2,185		1,883		1,509
Research and development		360		290		279
Total stock-based compensation	$	3,479	$	3,022	$	2,642

Schedule of Dividends Payable [Table Text Block]

Record Date	Payment Date	Per Share Amount		Dividend Payment
				(in thousands)
Fiscal Year 2021
March 9, 2021	March 25, 2021	$	0.110	$	2,262
May 19, 2021	June 3, 2021	$	0.110	$	2,267
August 26, 2021	September 9, 2021	$	0.110	$	2,401
November 19, 2021	December 2, 2021	$	0.110	$	2,405
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