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, 2016	Jan. 31, 2015
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	(1.38%)	0.09%
Effect of dividends received deductions	(0.70%)	(0.36%)
Domestic production tax credit	(0.54%)	(0.62%)
Write-off of goodwill		(1.85%)
Settlement of tax audits	(3.60%)
Other, net		0.09%
Effective income tax rate	28.78%	32.35%