REVENUE - Remaining Performance Obligations (Details) - USD ($)	Apr. 30, 2020	Apr. 30, 2019
Remaining performance obligations
Amount of remaining performance obligations	$ 10,726,000	$ 4,591,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-04-30
Remaining performance obligations
Amount of remaining performance obligations		$ 4,571,000
Remaining performance obligation		12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-04-30
Remaining performance obligations
Amount of remaining performance obligations	$ 4,659,000	$ 20,000
Remaining performance obligation	12 months	24 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-04-30
Remaining performance obligations
Amount of remaining performance obligations	$ 6,067,000
Remaining performance obligation	24 months