Income Taxes (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015
Income Tax Disclosure [Abstract]
Effective income tax rate	35.70%	33.70%	36.10%	33.50%
Federal research and experimentation tax credit			$ 1.2