Note 5 - Stock-based Compensation (Tables)

12 Months Ended

Mar. 31, 2019

Notes Tables

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

	Year Ended March 31
	2019			2018
Risk-free interest rate		2.9	%		1.8	%
Expected volatility		33	%		28	%
Expected life (years)		4.5			4.4
Dividend yield		3.7	%		5.3	%

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]

Ranges of Exercise Prices			Number Outstanding		Weighted Average Exercise Price		Weighted Remaining Contractual Life (years)
$49.86	-	$67.69		14,000	$	58.83		5.5
$76.13	-	$107.86		8,000		92.00		8.9
				22,000	$	70.89		6.7

Share-based Compensation, Activity [Table Text Block]

	Option Shares Reserved			Options Outstanding			Weighted Average Option Exercise Price
At March 31, 2017		143,230			19,000		$	57.51
Granted		(4,000	)		4,000		$	76.13
Exercised		-			(1,000	)	$	51.04
At March 31, 2018		139,230			22,000		$	61.19
Granted		(4,000	)		4,000		$	107.86
Exercised		-			(4,000	)	$	54.49
At March 31, 2019		135,230			22,000		$	70.89