Note 8 - Federal, State and Local Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Current tax expense:
Federal	$ 871	$ 1,140	$ 1,605	$ 2,459
State and local	72	169	160	248
Current tax expense	943	1,309	1,765	2,707
Deferred tax expense (benefit):
Federal	5	(126)	5	(312)
State and local	17	(119)	(254)	(149)
Deferred tax expense (benefit):	22	(245)	(249)	(461)
Income tax provision	$ 965	$ 1,064	$ 1,516	$ 2,246