Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Oct. 31, 2015	Oct. 31, 2014	Oct. 31, 2015	Oct. 31, 2014
Income Tax Disclosure [Abstract]
Effective income tax rate	36.30%	37.70%	36.20%	33.40%
Federal research and experimentation tax credit			$ 1.1