Loss Per Share and Stockholders' Equity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2016	Oct. 31, 2015	Oct. 31, 2016	Oct. 31, 2015
Antidilutive securities excluded from computation of earnings per share, amount (in shares)			4,600	5,000
Net loss from continuing operations attributable to shareholders	$ (143,415)	$ (142,518)	$ (264,441)	$ (239,023)
Amounts allocated to participating securities	(143)	(102)	(267)	(204)
Net loss from continuing operations attributable to common shareholders	$ (143,558)	$ (142,620)	$ (264,708)	$ (239,227)
Basic weighted average common shares (in shares)	215,535	266,267	218,009	271,016
Potential dilutive shares (in shares)	0	0	0	0
Weighted Average Number of Shares Outstanding, Diluted	215,535	266,267	218,009	271,016
Basic (in usd per share)	$ (0.67)	$ (0.54)	$ (1.21)	$ (0.88)
Narrative Details [Abstract]
Stock Repurchased and Retired During Period, Shares			9,600	40,500
Stock Repurchased and Retired During Period, Value			$ 217,020	$ 1,500,000
Accelerated Share Repurchases, Final Price Paid Per Share			$ 22.51	$ 37.00
Shares repurchased during the period, (in shares)			200	600
Shares repurchased during the period, Value			$ 5,600	$ 17,800
Shares issued during period (in shares)			900	1,800
Nonvested units granted			1,200
Stock-based compensation	$ 6,900	$ 7,900	$ 12,500	$ 13,900
Unrecognized compensation costs, options	100		100
Unrecognized compensation costs, nonvested shares and units	$ 41,200		41,200
Common Stock [Member]
Narrative Details [Abstract]
Stock Repurchased and Retired During Period, Value			96	405
Additional Paid-in Capital [Member]
Narrative Details [Abstract]
Stock Repurchased and Retired During Period, Value			5,784	24,325
Retained Earnings [Member]
Narrative Details [Abstract]
Stock Repurchased and Retired During Period, Value			$ 211,140	$ 1,475,270