Note 5 - Income Taxes - Reconciliation of Income Tax Provision (Details) - USD ($)	12 Months Ended
Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019
Income taxes at U.S. statutory rates	$ 8,235,000	$ 7,118,000	$ 10,315,000
State income taxes, net of federal tax benefit	708,000	649,000	1,233,000
Restricted stock (windfall) shortfall adjustment	(135,000)	322,000	(176,000)
Other	(195,000)	(47,000)	9,000
Total provision for income taxes	$ 8,613,000	$ 8,042,000	$ 11,381,000

Amount of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to expense for award under share-based payment arrangement. Excludes expense determined to be nondeductible upon grant or after for award under share-based payment arrangement.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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The amount of income tax expense or benefit for the period computed by applying the domestic federal statutory tax rates to pretax income from continuing operations.

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Amount of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax exempt income, equity in earnings (loss) of an unconsolidated subsidiary, minority noncontrolling interest income (loss), tax holiday, disposition of a business, disposition of an asset, repatriation of foreign earnings, repatriation of foreign earnings jobs creation act of 2004, increase (decrease) in enacted tax rate, prior year income taxes, increase (decrease) in deferred tax asset valuation allowance, and other adjustments.

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