Note 8 - Federal, State and Local Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Current tax expense:
Federal	$ 1,140	$ 996	$ 2,459	$ 4,573
State and local	169	15	248	340
Current tax expense	1,309	1,011	2,707	4,913
Deferred tax expense (benefit):
Federal	(126)	(399)	(312)	(588)
State and local	(119)	(76)	(149)	(61)
Deferred tax expense (benefit):	(245)	(475)	(461)	(649)
Income tax provision	$ 1,064	$ 536	$ 2,246	$ 4,264