Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions (Details)	6 Months Ended
	Oct. 31, 2016 USD ($) yr
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 1	$ 0
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 2	$ 0
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 3	1.10%
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 4	1.66%
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 5	$ 0
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 6	$ 0
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 7	95.19%
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 8	90.23%
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 9	$ 0
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 10	$ 0
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 11 | yr	3.7
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 12 | yr	3.7
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 13	$ 0
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 14	$ 0
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 15	0.00%
Common Stock Schedule Of Share-based Payment Award, Stock Options, Valuation Assumptions 16	0.00%