Investments (Detail Textuals) - USD ($)	9 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Apr. 30, 2015
Schedule of Available-for-sale Securities [Line Items]
Aggregate cost of equity securities available for sale	$ 4,625,000		$ 9,470,000
Proceeds from sales of equity securities classified as available-for-sale	8,789,000	$ 57,000
Capital losses	15,000
Fair value of equity securities	$ 4,550,000		9,632,000
Percentage of annual dividend return on investment	3.00%
Decrease in gross unrealized gains on equity securities classified as available-for-sale	$ (237,000)	(51,000)
Equity Securities
Schedule of Available-for-sale Securities [Line Items]
Aggregate cost of equity securities available for sale	4,625,000		9,470,000
Proceeds from sales of equity securities classified as available-for-sale	8,789,000	57,000
Capital losses	15,000
Fair value of equity securities	4,550,000		9,632,000
Decrease in gross unrealized gains on equity securities classified as available-for-sale		51,000
Deferred taxes on unrealized gains on securities		$ 18,000
Increase in gross unrealized losses on equity securities	237,000
Deferred taxes on unrealized losses on securities	84,000
Accumulated other comprehensive income included unrealized losses, net of tax	74,000		162,000
Deferred taxes on accumulated other comprehensive income	$ 26,000		$ 57,000