Federal, State and Local Income Taxes - Provision for income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2013
Current tax expense (benefit):
Federal	$ 3,197	$ 2,707	$ 2,679
State and local	243	239	130
Current tax expense (benefit)	3,440	2,946	2,809
Deferred tax expense (benefit):
Federal	(83)	572	728
State and local	(154)	(108)	350
Deferred tax expense (benefit)	(237)	464	1,078
Income tax provision:	$ 3,203	$ 3,410	$ 3,887