Federal, State and Local Income Taxes - Provision for income taxes differs from the amount of income tax determined by applying the applicable U.S. statutory income tax rate (Details 2)	6 Months Ended
	Oct. 31, 2013	Oct. 31, 2012
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
U.S. statutory federal rate	35.00%	35.00%
Increase (decrease) in tax rate from:
State and local income taxes, net of federal income tax benefit	2.23%	2.68%
Effect of dividends received deductions	(0.35%)	(0.25%)
Domestic production tax credit	(0.40%)	(0.59%)
Other, net	(0.12%)	0.34%
Effective income tax rate	36.36%	37.18%