Earnings Per Share (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Apr. 30, 2014	Jan. 31, 2014	Oct. 31, 2013	Jul. 31, 2013	Apr. 30, 2013	Jan. 31, 2013	Oct. 31, 2012	Jul. 31, 2012	Apr. 30, 2014	Apr. 30, 2013	Apr. 30, 2012
Earnings Per Share [Abstract]
Net income from continuing operations attributable to shareholders	$ 929,133	$ (212,751)	$ (103,015)	$ (113,270)	$ 688,922	$ (16,915)	$ (101,199)	$ (105,650)	$ 500,097	$ 465,158	$ 345,968
Amounts allocated to participating securities									(692)	(542)	(455)
Net income from continuing operations attributable to common shareholders									$ 499,405	$ 464,616	$ 345,513
Basic weighted average common shares (in shares)									273,830,000	273,057,000	297,863,000
Potential dilutive shares									2,197,000	1,302,000	738,000
Dilutive weighted average common shares									276,027,000	274,359,000	298,601,000
Basic (in usd per share)	$ 3.38	$ (0.78)	$ (0.38)	$ (0.42)	$ 2.53	$ (0.06)	$ (0.37)	$ (0.38)	$ 1.82	$ 1.70	$ 1.16
Diluted (in usd per share)	$ 3.36	$ (0.78)	$ (0.38)	$ (0.42)	$ 2.51	$ (0.06)	$ (0.37)	$ (0.38)	$ 1.81	$ 1.69	$ 1.16
Antidilutive securities excluded from computation of earnings per share, amount									100,000	3,300,000	8,900,000