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)	9 Months Ended
	Jan. 31, 2013	Jan. 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	2.78%	2.73%
Effect of dividends received deductions	(0.26%)	(0.11%)
Domestic production tax credit	(0.58%)
Other, net		0.20%
Effective income tax rate	36.94%	37.82%