Federal, State and Local Income Taxes - Provision for income taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012
Current tax expense (benefit):
Federal	$ 727	$ 414	$ 2,054	$ 371
State and local	156	131	258	(84)
Current tax expense (benefit)	883	545	2,312	287
Deferred tax expense (benefit):
Federal	97	448	533	2,784
State and local	23	445	140	478
Deferred tax expense (benefit)	120	893	673	3,262
Income tax provision:	$ 1,003	$ 1,438	$ 2,985	$ 3,549