Note 9 - Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2018

Notes Tables

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

	2018			2017			2016
Dividend yield		1.2	%		0.7	%		1.3	%
Volatility		41.3	%		39.1	%		34.5	%
Risk-free interest rate		2.7	%		2.2	%		1.2	%
Weighted average expected option term (in years)		4.8			4.6			5.5
Weighted average fair value per share of options granted	$	8.28		$	10.37		$	4.04

Share-based Compensation, Stock Options, 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, 2017 (1)		1,536,282		$	13.86		4.15	$	27,771,635
Granted		280,423		$	23.56
Exercised (2)		(303,379	)	$	9.79			$	7,196,175
Canceled / Expired		(50,751	)	$	13.79
Balance outstanding at December 31, 2018 (3)		1,462,575		$	16.41		4.54	$	12,214,422
Vested and exercisable at December 31, 2018 (4)		504,988		$	11.51		2.65	$	6,482,151
Expected to vest at December 31, 2018		957,587		$	18.99		5.54
Total		1,462,575

Schedule of Share-based Compensation, Restricted Stock Units Award Activity [Table Text Block]

				Weighted
				Average
				Grant Date
	Shares			Fair Value
Balance outstanding at December 31, 2017		216,750		$	18.10
Granted		87,088		$	23.65
Vested (1)		(63,478	)	$	15.11
Canceled		(22,465	)	$	17.75
Balance outstanding at December 31, 2018		217,895		$	21.21

Accelerated Share Repurchases [Table Text Block]

	2018		2017
Shares of common stock repurchased		21,410		27,291
Average per share repurchase price	$	34.62	$	28.51
Aggregage purchase price (in thousands)	$	741	$	778

Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]

	2018		2017		2016
	(in thousands)
Stock option awards	$	1,457	$	1,612	$	1,116
Restricted stock units		892		644		564
Total stock-based compensation	$	2,349	$	2,256	$	1,680

	2018		2017		2016
	(in thousands)
Cost of sales	$	272	$	188	$	175
Sales and marketing		529		403		373
General and administrative		1,293		1,484		983
Research and development		255		181		149
Total stock-based compensation	$	2,349	$	2,256	$	1,680

Schedule of Dividends Payable [Table Text Block]

Record Date	Payment Date	Per Share Amount		Dividend Payment
				(in thousands)
Fiscal Year 2018
March 22, 2018	April 5, 2018	$	0.070	$	1,351
May 22, 2018	June 7, 2018	$	0.070	$	1,353
August 22, 2018	September 6, 2018	$	0.070	$	1,369
November 20, 2018	December 6, 2018	$	0.070	$	1,372
Fiscal Year 2017
March 22, 2017	April 6, 2017	$	0.055	$	1,029
May 24, 2017	June 8, 2017	$	0.055	$	1,036
August 23, 2017	September 6, 2017	$	0.055	$	1,055
November 22, 2017	December 7, 2017	$	0.055	$	1,060