Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended	9 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Oct. 31, 2017	Jan. 31, 2018	Jan. 31, 2017	Apr. 30, 2017
Income Tax Disclosure [Abstract]
Income taxes (benefit)	$ 122,120	$ (49,386)	$ 165,400	$ (43,234)	$ (216,963)
Effective Income Tax Rate Reconciliation, Amount [Abstract]
U.S. statutory tax rate				21.00%	35.00%
State income taxes, net of federal income tax benefit				2.20%	1.60%
Earnings taxed in foreign jurisdictions				(2.30%)	(5.30%)
Permanent differences				0.30%	(0.50%)
Uncertain tax positions				6.00%	6.50%
Remeasurement of deferred tax assets and liabilities				2.40%	0.00%
Tax benefit due to effective date of statutory rate change				(16.40%)	0.00%
One-time transition tax				(2.40%)	0.00%
Other				(3.10%)	(0.10%)
Effective tax rate			37.50%	7.70%	37.20%
Loss from continuing operations	(120,805)	(150,598)	$ 441,500	$ (562,289)	$ (582,616)
Unrecognized tax benefits	163,100	$ 97,100		163,100	97,100	$ 149,900
Gross unrecognized tax benefits increase (decrease)				13,100	$ (14,400)
Change in tax benefits that are reasonably possible	17,400			17,400
Effect of anticipated settlements of audit issues and expiring statutes of limitations	$ 15,100			$ 15,100
Decrease in deferred tax assets			$ 58,400