Stock-Based Compensation (Schedule of Stock Options and SSARs) (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	12 Months Ended
	Apr. 30, 2014
Stock Options and SSARs, Number of Underlying Shares [Roll Forward]
Stock options and SSARs oustanding, Beginning balance (shares)	4,587
Stock options and SSARs outstanding, Granted (shares)	414
Stock options and SSARs outstanding, Exercised (shares)	(919)
Stock options and SSARs outstanding, Forfeited or expired (shares)	(19)
Stock options and SSARs oustanding, Ending balance (shares)	4,063
Stock Options and SSARs, Weighted Average Exercise Price [Roll Forward]
Stock options and SSARs outstanding, Weighted Average Exercise Price Per Award, Beginning balance (dollars per share)	$ 37.22
Stock options and SSARs outstanding, Weighted Average Exercise Price Per Award, Granted (dollars per share)	$ 72.42
Stock options and SSARs outstanding, Weighted Average Exercise Price Per Award, Exercised (dollars per share)	$ 29.63
Stock options and SSARs outstanding, Weighted Average Exercise Price Per Award, Forfeited or expired (dollars per share)	$ 55.23
Stock options and SSARs outstanding, Weighted Average Exercise Price Per Award, Ending balance (dollars per share)	$ 42.44
Stock options and SSARs outstanding, Weighted Average Remaining Contractual Term (years)	5 years 1 month 3 days
Stock options and SSARs outstanding, Aggregate Intrinsic Value	$ 193
Stock options and SSARs Exercisable (shares)	2,537
Stock options and SSARs Exercisable, Weighted Average Exercise Price Per Award (dollars per share)	$ 33.31
Stock options and SSARs Exercisable, Weighted Average Remaining Contractual Term (years)	3 years 6 months 28 days
Stock options and SSARs Exercisable, Aggregate Intrinsic Value	$ 143