Note 14 - Stock Option Plans (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

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

	Year Ended December 31,
	2019			2018			2017
Volatility		36.5	%		37.9	%		41.6	%
Risk-free interest rate		2.0	%		2.7	%		1.8	%
Expected life (in years)		4.50			4.48			4.55
Dividend yield		0.0	%		0.0	%		0.0	%
The weighted average grant date fair value for options issued, with the exercise price equal to market value on the date of grant	$	20.20		$	22.22		$	20.08

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

	Twelve months ended December 31, 2019					Twelve months ended December 31, 2018					Twelve months ended December 31, 2017
	Number of shares			Weighted average exercise price per share		Number of shares			Weighted average exercise price per share		Number of shares			Weighted average exercise price per share
Outstanding, beginning of period		702,337		$	43.80		653,571		$	36.69		474,501		$	12.67
Granted		180,800			60.56		163,366			62.80		370,025			54.10
Exercised		(80,319	)		16.90		(63,886	)		12.86		(172,759	)		7.88
Forfeited		(31,986	)		59.35		(50,714	)		52.33		(18,196	)		37.70
Expired		(16,335	)		47.51		-			-		-			-
Outstanding, end of period		754,497			49.94		702,337			43.80		653,571			36.69
Options exercisable, end of period		356,066		$	40.64		326,937		$	28.91		243,771		$	14.79

Share-based Payment Arrangement, Option, Exercise Price Range [Table Text Block]

	Options outstanding								Options exercisable
Exercise price	Number outstanding		Weighted average exercise price per share		Weighted average remaining contractual life (years)		Aggregate intrinsic value		Number exercisable		Weighted average exercise price per share		Weighted average remaining contractual life (years)		Aggregate intrinsic value
$ 8.56 - $ 8.56		19,535	$	8.56		0.4	$	1,040		19,535	$	8.56		0.4	$	1,039
$10.16 - $19.95		74,465		16.42		1.7		3,378		73,215		16.36		1.7		3,326
$21.10 - $27.53		58,750		23.73		2.1		2,236		48,750		24.27		1.9		1,829
$35.25 - $37.35		14,375		35.89		3.4		372		11,875		36.02		3.3		306
$47.00 - $47.00		5,000		47.00		4.2		74		2,500		47.00		4.2		37
$53.20 - $58.65		340,078		55.53		4.5		2,124		172,802		55.68		4.2		1,053
$61.33 - $64.10		242,294		62.99		6.0		-		27,389		64.10		5.4		-
		754,497	$	49.94		4.4	$	9,224		356,066	$	40.64		3.2	$	7,590

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

	Year Ended December 31,
	2019		2018		2017
Network expenses	$	307	$	223	$	110
Sales and marketing		1,251		1,025		573
Technical operations and development		596		636		360
General and administrative		722		690		414
	$	2,876	$	2,574	$	1,457