Stock Award Plan (Details) (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended		12 Months Ended	0 Months Ended	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013	Jul. 31, 2013	Oct. 11, 2011 Class A [Member]	Jul. 31, 2013 Class A [Member]
Class of Stock [Line Items]
Shares awarded (in shares)				62,099	16,387
Shares awarded, value				$ 0.9	$ 0.2
Share-based award, vesting period	3 years
Compensation expense	0.3	0.4
Unrecognized compensation expense	0.2
Excess tax benefits accumulated in Capital in Excess of Par Value	$ 0.2		$ 0.3