Revenue Recognition (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended
	Jan. 31, 2019	Apr. 30, 2018	Jan. 31, 2018	Apr. 30, 2017
POM
Disaggregation of Revenue [Line Items]
Current deferred revenue	$ 105,300
Expected recognition period	60 months
TIS
Disaggregation of Revenue [Line Items]
Current deferred revenue	$ 21,300	$ 36,400	$ 27,000	$ 20,600
Expected recognition period	15 months
Deferred Revenue | POM
Disaggregation of Revenue [Line Items]
Description of timing	The plan is effective for the life of the tax return, which can be up to six years; however, the majority of claims are incurred in years two and three after the sale of POM.
Deferred revenue	$ 155,546	$ 218,274	$ 153,899	$ 211,223