Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Operating Loss Carryforwards [Line Items]
Accelerated depreciation	$ 8,500
Impairment of goodwill	$ 106,000	$ 0	$ 0
Effective tax rate	282.40%	18.30%	6.30%
Income (loss) from continuing operations before taxes (benefit)	$ (3,374)	$ 545,160	$ 668,732
Net loss	13,682	22,747	13,760
Tax benefits from discontinued operations	4,085	6,788	7,016
Valuation allowance, decrease in deferred tax asset	(1,900)
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction	4,100
SEC Schedule, 12-09, Valuation Allowances and Reserves, Additions, Charge to Cost and Expense	2,200
Net NOL DTAs	45,000
Net NOL DTAs subject to expiration	5,900
Net NOL DTAs not subject to expiration	39,100
Unrecognized tax benefits that would impact effective tax rate	132,300	122,500	132,400
Amount of unrecorded benefit	12,200
Total gross interest and penalties accrued	22,000	$ 22,400	$ 18,700
State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, valuation allowance	22,800
Foreign
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards, valuation allowance	$ 22,200