Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2014	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2013	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2013
Earnings Per Share [Abstract]
Net income from continuing operations attributable to shareholders	$ 744,133	$ (35,311)	$ (113,227)	$ (108,851)	$ 929,133	$ (212,751)	$ (103,015)	$ (113,270)	$ 486,744	$ 500,097	$ 465,158
Amounts allocated to participating securities									774	692	542
Net income from continuing operations attributable to common shareholders									$ 485,970	$ 499,405	$ 464,616
Basic weighted average common shares (in shares)									275,033,000	273,830,000	273,057,000
Potential dilutive shares									2,103,000	2,197,000	1,302,000
Dilutive weighted average common shares									277,136,000	276,027,000	274,359,000
Basic (in usd per share)	$ 2.70	$ (0.13)	$ (0.41)	$ (0.40)	$ 3.38	$ (0.78)	$ (0.38)	$ (0.42)	$ 1.77	$ 1.82	$ 1.70
Diluted (in usd per share)	$ 2.68	$ (0.13)	$ (0.41)	$ (0.40)	$ 3.36	$ (0.78)	$ (0.38)	$ (0.42)	$ 1.75	$ 1.81	$ 1.69
Antidilutive securities excluded from computation of earnings per share, amount									100,000	100,000	3,300,000