Organization, Use of Estimates and Basis of Presentation - Calculation of Earnings Per Share (Details) - USD ($)	3 Months Ended		9 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Basic loss per share computation
Net loss attributable to common stockholders	$ (76,000)	$ (1,408,904)	$ (844,000)	$ (4,459,773)
Weighted average common shares outstanding, basic (in shares)	10,994,434	10,967,738	10,987,797	10,130,460
Basic and diluted net loss per share (in dollars per share)	$ (0.01)	$ (0.13)	$ (0.08)	$ (0.44)