Stock-Based Compensation (Schedule of Stock Options and SSARs) (Details) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Apr. 30, 2016 USD ($) $ / shares shares
Stock Options and SSARs, Number of Underlying Shares [Roll Forward]
Stock options and SSARs oustanding, Beginning balance (shares) | shares	3,817
Stock options and SSARs outstanding, Granted (shares) | shares	378
Stock options and SSARs outstanding, Exercised (shares) | shares	(758)
Stock options and SSARs outstanding, Forfeited or expired (shares) | shares	(11)
Stock options and SSARs oustanding, Ending balance (shares) | shares	3,426
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) | $ / shares	$ 48.46
Stock options and SSARs outstanding, Weighted Average Exercise Price Per Award, Granted (dollars per share) | $ / shares	102.25
Stock options and SSARs outstanding, Weighted Average Exercise Price Per Award, Exercised (dollars per share) | $ / shares	36.88
Stock options and SSARs outstanding, Weighted Average Exercise Price Per Award, Forfeited or expired (dollars per share) | $ / shares	87.71
Stock options and SSARs outstanding, Weighted Average Exercise Price Per Award, Ending balance (dollars per share) | $ / shares	$ 56.83
Stock options and SSARs outstanding, Weighted Average Remaining Contractual Term (years)	4 years 11 months 15 days
Stock options and SSARs outstanding, Aggregate Intrinsic Value | $	$ 138
Stock options and SSARs Exercisable (shares) | shares	2,293
Stock options and SSARs Exercisable, Weighted Average Exercise Price Per Award (dollars per share) | $ / shares	$ 41.24
Stock options and SSARs Exercisable, Weighted Average Remaining Contractual Term (years)	3 years 7 months 24 days
Stock options and SSARs Exercisable, Aggregate Intrinsic Value | $	$ 126