Earnings (loss) per common share (EPS) (Narrative) (Details)	6 Months Ended
	Oct. 31, 2017 shares
Earnings (loss) Per Common Share (eps) 1	820,886
Earnings (loss) Per Common Share (eps) 2	923,102
Earnings (loss) Per Common Share (eps) 3	3,677
Earnings (loss) Per Common Share (eps) 4	401,138