Revenue Recognition (Deferred Revenue) (Details) - USD ($) $ in Thousands	6 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Apr. 30, 2018	Apr. 30, 2017
POM
Disaggregation of Revenue [Line Items]
Contract with Customer, Liability, Current	$ 105,700
POM | Deferred Revenue
Movement in Deferred Revenue [Roll Forward]
Balance, beginning of the period	218,274	$ 211,223
Amounts deferred	3,459	2,913
Amounts recognized on previous deferrals	(71,074)	(63,332)
Balance, end of the period	150,659	150,804
POM | Deferred Wages
Movement in Deferred Revenue [Roll Forward]
Balance, beginning of the period	32,683	31,344
Amounts deferred	80	36
Amounts recognized on previous deferrals	(10,752)	(9,230)
Balance, end of the period	22,011	22,150
Revenues from Tax Identity Shield®
Disaggregation of Revenue [Line Items]
Contract with Customer, Liability, Current	$ 21,800	$ 24,400	$ 36,400	$ 20,600