Organization and Significant Accounting Policies Contract Estimates (Details) - USD ($)	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2017	Apr. 30, 2018
Material adjustment to any one contract	$ 0	$ 0
Revision of estimate of total costs required to complete the contracts | Cumulative catch-up adjustment
Amount of revised aggregate impact of adjustments in contract estimates on revenue related to performance obligations satisfied or partially satisfied in previous periods			$ 1,255,000