Property And Equipment (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Property, Plant and Equipment [Line Items]
Depreciation expense for capitalized software	$ 11.3	$ 9.0	$ 6.0
Net book value of capitalized software	$ 32.3	$ 28.7