Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Apr. 30, 2017	Jan. 31, 2017	Oct. 31, 2016	Jul. 31, 2016	Apr. 30, 2016	Jan. 31, 2016	Oct. 31, 2015	Jul. 31, 2015	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Earnings Per Share [Abstract]
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent									$ 420,917	$ 383,553	$ 486,744
Amounts allocated to participating securities									1,005	718	774
Net income from continuing operations attributable to common shareholders									$ 419,912	$ 382,835	$ 485,970
Basic weighted average common shares (in shares)									212,809	249,009	275,033
Potential dilutive shares									1,286	1,809	2,103
Dilutive weighted average common shares									214,095	250,818	277,136
Basic (in usd per share)	$ 3.79	$ (0.49)	$ (0.67)	$ (0.55)	$ 3.15	$ (0.34)	$ (0.54)	$ (0.35)	$ 1.97	$ 1.54	$ 1.77
Diluted (in usd per share)	$ 3.76	$ (0.49)	$ (0.67)	$ (0.55)	$ 3.13	$ (0.34)	$ (0.54)	$ (0.35)	$ 1.96	$ 1.53	$ 1.75
Antidilutive securities excluded from computation of earnings per share, amount									300	100	100