Loss Per Share and Stockholders' Equity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Jul. 31, 2017	Jul. 31, 2016
Earnings Per Share [Abstract]
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	2,800	4,700
Net loss from continuing operations attributable to shareholders	$ (127,818)	$ (121,026)
Amounts allocated to participating securities	(160)	(124)
Net loss from continuing operations attributable to common shareholders	$ (127,978)	$ (121,150)
Basic weighted average common shares (in shares)	207,935	220,484
Potential dilutive shares (in shares)	0	0
Weighted Average Number of Shares Outstanding, Diluted	207,935	220,484
Basic (in usd per share)	$ (0.62)	$ (0.55)
Narrative Details [Abstract]
Stock Repurchased and Retired During Period, Shares		2,000
Stock Repurchased and Retired During Period, Value		$ 48,600
Accelerated Share Repurchases, Final Price Paid Per Share		$ 23.84
Shares repurchased during the period, (in shares)	200	200
Shares repurchased during the period, Value	$ 7,500	$ 5,600
Shares issued during period (in shares)	2,100	900
Nonvested units granted	600
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Stock-based compensation	$ 4,800	$ 5,500
Unrecognized compensation costs, options	100
Unrecognized compensation costs, nonvested shares and units	$ 40,300