Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended		48 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014	Oct. 31, 2013	Apr. 30, 2014
Income Tax Disclosure [Abstract]
Effective income tax rate	37.70%	38.90%	33.40%	38.20%
Federal research and experimentation tax credit					$ 1.1