Stock-Based Compensation SSARs (Details) - Stock Appreciation Rights (SARs) [Member] $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Apr. 30, 2019 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
SSARs outstanding, beginning balance (shares) | shares	7,215
SSARs granted (shares) | shares	605
SSARs exercised (shares) | shares	(903)
SSARs forfeited or expired (shares) | shares	(65)
SSARs outstanding, ending balance (shares) | shares	6,852
SSARs exercisable (shares) | shares	4,381
Weighted Average Fair Value at Grant Date [Roll Forward]
Weighted average exercise price, beginning (dollars per share) | $ / shares	$ 29.67
Weighted average exercise price, grants in period (dollars per share) | $ / shares	54.00
Weighted average exercise price, exercises in period (dollars per share) | $ / shares	17.13
Weighted average exercise price, forfeitures and expirations in period (dollars per share) | $ / shares	52.49
Weighted average exercise price, ending (dollars per share) | $ / shares	33.25
Weighted average exercise price, exercisable (dollars per share) | $ / shares	$ 28.10
SSARs outstanding, Weighted Average Remaining Contractual Term (years)	4 years 11 months 4 days
SSARs exercisable, Weighted Average Remaining Contractual Term (years)	3 years 7 months 17 days
SSARs outstanding, Aggregate Intrinsic Value | $	$ 138
SSARs exercisable, Aggregate Intrinsic Value | $	$ 110