Note 11 - Share-based Compensation (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
	Common Stock (former Class A)			Common Stock (former Class A)			Former Class B Common Stock			Common Stock (former Class A)			Former Class B Common Stock
Expected dividend yield at date of grant		2.59	%		2.62	%		8.06	%		2.99	%		7.29	%
Expected stock price volatility		32.47	%		32.45	%		26.75	%		32.74	%		29.41	%
Risk-free interest rate		2.51	%		2.18	%		2.18	%		1.69	%		1.69	%
Expected life of options (in years)		7.28			6.80			6.80			6.86			6.86

Share-based Compensation, Activity [Table Text Block]

	Number of Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Terms (Years)		Aggregate Intrinsic Value (In thousands)
Common Stock (former Class A)
Outstanding at December 31, 2017		1,746,634		$	13.88
Granted		116,276		$	36.12
Exercised		(468,318	)	$	12.67			$	10,621
Forfeited		(21,383	)	$	26.18
Outstanding at December 31, 2018		1,373,209		$	15.99		4.91	$	30,421
Exercisable at December 31, 2018		981,069		$	13.76		3.83	$	23,923
Former Class B Common Stock
Outstanding at December 31, 2017		276,716		$	31.78
Granted		--		$	--
Exercised/Settled in Recapitalization		(276,716	)	$	31.78		--	$	5,937
Forfeited		--		$	--
Outstanding at December 31, 2018		--		$	--		--	$	--
Exercisable at December 31, 2018		--		$	--		--	$	--

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

	2018		2017				2016
	Common Stock (former Class A)		Common Stock (former Class A)		Former Class B Common Stock		Common Stock (former Class A)		Former Class B Common Stock
Weighted average grant date fair value of stock options granted	$	10.02	$	5.83	$	3.66	$	3.62	$	3.90
Intrinsic value of stock options exercised (in thousands)	$	10,621	$	2,681	$	202	$	459	$	632
Intrinsic value of stock options vested (in thousands)	$	2,719	$	5,258	$	787	$	1,627	$	535

Schedule of Nonvested Share Activity [Table Text Block]

	Common Stock (formerly Class A) Outstanding			Common Stock (formerly Class A) Weighted Average Grant Date Fair Value Per Share		Former Class B Common Stock Outstanding			Former Class B Common Stock Weighted Average Grant Date Fair Value Per Share
Outstanding at December 31, 2017		81,667		$	13.80		13,611		$	36.65
Granted		6,793		$	36.80		--		$	--
Vested		--		$	--		(13,611	)	$	36.65
Forfeited		(10,289	)	$	15.23		--		$	--
Outstanding at December 31, 2018		78,171		$	15.61		--		$	--