Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2014	Jul. 31, 2014	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Earnings Per Share [Abstract]
Net income from continuing operations attributable to shareholders	$ 701,225	$ (78,649)	$ (142,518)	$ (96,505)	$ 744,133	$ (35,311)	$ (113,227)	$ (108,851)	$ 383,553	$ 486,744	$ 500,097
Amounts allocated to participating securities									718	774	692
Net income from continuing operations attributable to common shareholders									$ 382,835	$ 485,970	$ 499,405
Basic weighted average common shares (in shares)									249,009	275,033	273,830
Potential dilutive shares									1,809	2,103	2,197
Dilutive weighted average common shares									250,818	277,136	276,027
Basic (in usd per share)	$ 3.15	$ (0.34)	$ (0.54)	$ (0.35)	$ 2.70	$ (0.13)	$ (0.41)	$ (0.40)	$ 1.54	$ 1.77	$ 1.82
Diluted (in usd per share)	$ 3.13	$ (0.34)	$ (0.54)	$ (0.35)	$ 2.68	$ (0.13)	$ (0.41)	$ (0.40)	$ 1.53	$ 1.75	$ 1.81
Antidilutive securities excluded from computation of earnings per share, amount									100