Note 7 - Income Taxes (Details Textual) - USD ($)	3 Months Ended		6 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Tax Expense (Benefit)	$ 3,880,000	$ 2,887,000	$ 9,344,000	$ 6,774,000
Effective Income Tax Rate Reconciliation, Percent	30.70%	37.10%	34.10%	37.10%
Restricted Stock [Member]
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ 807,000		$ 807,000