Loss Per Share and Stockholders' Equity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)			3,400	4,600
Net loss from continuing operations attributable to shareholders	$ (148,312)	$ (143,415)	$ (276,130)	$ (264,441)
Amounts allocated to participating securities	(161)	(143)	(321)	(267)
Net loss from continuing operations attributable to common shareholders	$ (148,473)	$ (143,558)	$ (276,451)	$ (264,708)
Basic weighted average common shares (in shares)	209,065	215,535	208,500	218,009
Potential dilutive shares (in shares)	0	0	0	0
Weighted Average Number of Shares Outstanding, Diluted	209,065	215,535	208,500	218,009
Basic (in usd per share)	$ (0.71)	$ (0.67)	$ (1.33)	$ (1.21)
Narrative Details [Abstract]
Stock Repurchased and Retired During Period, Shares				9,600
Stock Repurchased and Retired During Period, Value				$ 217,000
Accelerated Share Repurchases, Final Price Paid Per Share				$ 22.51
Shares repurchased during the period, (in shares)			200	200
Shares repurchased during the period, Value			$ 7,600	$ 5,600
Shares issued during period (in shares)			2,100	900
Nonvested units granted			1,200
Stock-based compensation	$ 6,800	$ 6,900	$ 11,600	$ 12,500
Unrecognized compensation costs, options	1,300		1,300
Unrecognized compensation costs, nonvested shares and units	$ 42,300		$ 42,300