Note 18 - Equity Incentive Plan (Tables)

12 Months Ended

Dec. 31, 2019

Notes Tables

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

	2019			2018			2017
Expected dividends		1.60	%		1.22	%		1.27	%
Expected term (in years)		7.14			9.35			7.79
Expected stock price volatility		25	%		24	%		26	%
Risk-free rate		1.90	%		2.83	%		2.23	%

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

	2019					2018					2017
				Weighted Average					Weighted Average					Weighted Average
	Shares			Exercise Price		Shares			Exercise Price		Shares			Exercise Price
Outstanding at beginning of year		277,820		$	40.11		285,780		$	39.31		183,747		$	38.09
Granted		17,833			51.16		21,666			46.59		112,333			40.87
Exercised		(22,614	)		35.78		(22,460	)		37.07		(5,078	)		29.65
Forfeited or expired		0			0		(7,166	)		37.53		(5,222	)		39.22
Outstanding at end of year		273,039		$	41.19		277,820		$	40.11		285,780		$	39.31
Options and cash-settled SARs exercisable at year end		122,932		$	40.19		94,951		$	39.14		42,256		$	36.66

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

	Options and Cash-Settled SARs Outstanding						Options and Cash-Settled SARs Exercisable
					Weighted Average						Weighted Average
Range of	Number				Remaining		Number				Remaining
Exercise	Outstanding at		Weighted Average		Contractual Term (In		Exercisable at		Weighted Average		Contractual Term (In
Prices	12/31/19		Exercise Price		Years)		12/31/19		Exercise Price		Years)
$28.00 - $38.00		20,065	$	32.66		2.98		8,487	$	32.35		2.78
$38.01 - $51.25		252,974	$	41.86		6.68		114,445	$	40.77		5.74
		273,039						122,932
Aggregate intrinsic value (in thousands)	$	3,703					$	1,790