Note 9 - Share-based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

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

	2019			2018			2017
	Common Stock			Common Stock			Common Stock (former Class A)			Former Class B Common Stock
Expected dividend yield at date of grant		2.60	%		2.59	%		2.62	%		8.06	%
Expected stock price volatility		34.01	%		32.47	%		32.45	%		26.75	%
Risk-free interest rate		2.38	%		2.51	%		2.18	%		2.18	%
Expected life of options (in years)		7.46			7.28			6.80			6.80

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

	Number of Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Terms (Years)		Aggregate Intrinsic Value (In thousands)
Common Stock
Outstanding at December 31, 2018		1,373,209		$	15.99
Granted		100,615		$	41.64
Exercised		(227,902	)	$	15.88			$	8,280
Forfeited		--		$	--
Outstanding at December 31, 2019		1,245,922		$	18.08		4.45	$	59,631
Exercisable at December 31, 2019		807,537		$	14.33		3.02	$	41,677

Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value, Intrinsic Value of Exercised and Vested in Period, and Fair Value of Vested in Period [Table Text Block]

	2019		2018		2017
	Common Stock		Common Stock (former Class A)		Common Stock (former Class A)		Former Class B Common Stock
Weighted average grant date fair value of stock options granted	$	11.99	$	10.02	$	5.83	$	3.66
Intrinsic value of stock options exercised (in thousands)	$	8,280	$	10,621	$	2,681	$	202
Intrinsic value of stock options vested (in thousands)	$	1,891	$	2,719	$	5,258	$	787

Schedule of Nonvested Share Activity [Table Text Block]

	Common Stock Outstanding		Common Stock Weighted Average Grant Date Fair Value Per Share
Outstanding at December 31, 2018		78,171	$	15.61
Granted		6,005	$	38.30
Vested		--	$	--
Forfeited		--	$	--
Outstanding at December 31, 2019		84,176	$	17.23