Stock-Based Compensation SSARs (Details) - Stock Appreciation Rights (SARs) [Member] $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Apr. 30, 2020 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
SSARs outstanding, beginning balance (shares) | shares	6,852
SSARs granted (shares) | shares	522
SSARs exercised (shares) | shares	(2,434)
SSARs forfeited or expired (shares) | shares	(10)
SSARs outstanding, ending balance (shares) | shares	4,930
SSARs exercisable (shares) | shares	2,932
Weighted Average Fair Value at Grant Date [Roll Forward]
Weighted average exercise price, beginning (dollars per share) | $ / shares	$ 33.25
Weighted average exercise price, grants in period (dollars per share) | $ / shares	54.64
Weighted average exercise price, exercises in period (dollars per share) | $ / shares	27.77
Weighted average exercise price, forfeitures and expirations in period (dollars per share) | $ / shares	49.70
Weighted average exercise price, ending (dollars per share) | $ / shares	38.19
Weighted average exercise price, exercisable (dollars per share) | $ / shares	$ 31.86
SSARs outstanding, Weighted Average Remaining Contractual Term (years)	5 years 1 month 6 days
SSARs exercisable, Weighted Average Remaining Contractual Term (years)	3 years 8 months 12 days
SSARs outstanding, Aggregate Intrinsic Value | $	$ 118
SSARs exercisable, Aggregate Intrinsic Value | $	$ 89