Federal, State and Local Income Taxes - Provision for income taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Current tax expense (benefit):
Federal	$ 2,679	$ 139	$ 356
State and local	130	(54)	(413)
Current tax expense (benefit)	2,809	85	(57)
Deferred tax expense:
Federal	728	3,785	20,535
State and local	350	503	3,203
Deferred tax expense	1,078	4,288	23,738
Income tax provision	$ 3,887	$ 4,373	$ 23,681

Amount of current federal tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of current income tax expense (benefit) pertaining to taxable income (loss) from continuing operations.

Amount of current state and local tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred federal income tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred income tax expense (benefit) pertaining to income (loss) from continuing operations.

Amount of deferred state and local tax expense (benefit) pertaining to income (loss) from continuing operations.