Earnings Per Share - Schedule of Basic and Diluted Earnings Per Share (Details) - USD ($)	3 Months Ended		9 Months Ended
	Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019
Earnings Per Share [Abstract]
Net income attributable to common stockholders	$ 1,799,805	$ 59,118	$ 2,546,483	$ 789,399
Weighted-average shares outstanding - basic	28,361,201	28,361,201	28,361,201	28,361,201
Incremental shares from assumed conversion of warrants and options	638,298	650,847	642,000	648,214
Diluted shares	28,999,499	29,012,048	29,003,201	29,009,415
Income per share - Basic and Diluted	$ 0.06	$ 0.00	$ 0.09	$ 0.03