Note 5 - Stock-based Compensation (Tables)

12 Months Ended

Mar. 31, 2021

Notes Tables

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

	Year Ended March 31
	2021			2020
Risk-free interest rate	0.2	–	0.4%		1.7	%
Expected volatility	34	–	35%		37	%
Expected life (years)		4.6			4.6
Dividend yield	7.0	–	7.4%		5.9	%

Share-based Payment Arrangement, Option, 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		22,000	$	59.85		5.3
$76.13	–	$107.86		8,000		92.00		6.9
				30,500	$	68.28		5.7

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

	Option Shares Reserved			Options Outstanding			Weighted Average Option Exercise Price
At March 31, 2019		135,230			22,000		$	70.89
Granted		(4,000	)		4,000		$	67.65
Exercised		-			(2,000	)	$	56.18
At March 31, 2020		131,230			24,000		$	71.58
Granted		(6,500	)		6,500		$	56.12
At March 31, 2021		124,730			30,500		$	68.28