Preferred and Common Stock - Schedule of Stock Options Activity (Details) - $ / shares	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Number of option shares
Ending balance (in shares)	109,827
Stock Options
Number of option shares
Beginning balance (in shares)	181,673	222,050	291,200
Granted (in shares)	0	0	0
Exercised (in shares)	(71,546)	(40,377)	(69,150)
Forfeited (in shares)	(300)	0	0
Ending balance (in shares)	109,827	181,673	222,050
Weighted average option exercise price
Beginning balance (in Dollars per share)	$ 39.48	$ 38.51	$ 37.46
Granted (in Dollars per share)	0.00	0.00	0.00
Exercised (in Dollars per share)	32.02	34.11	34.08
Forfeited (in Dollars per share)	25.26	0.00	0.00
Ending balance (in Dollars per share)	$ 44.39	$ 39.48	$ 38.51