Stock-Based Compensation SSARs (Details) - Stock Appreciation Rights (SARs) [Member] $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Apr. 30, 2021 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Outstanding, beginning balance (shares) | shares	4,930
SSARs granted (shares) | shares	448
SSARs exercised (shares) | shares	(1,064)
SSARs forfeited or expired (shares) | shares	(3)
Outstanding, ending balance (shares) | shares	4,311
SSARs exercisable (shares) | shares	2,805
Weighted Average Exercise Price [Roll Forward]
Weighted average exercise price, beginning (dollars per share) | $ / shares	$ 38.19
Weighted average exercise price, grants in period (dollars per share) | $ / shares	69.21
Weighted average exercise price, exercises in period (dollars per share) | $ / shares	29.53
Weighted average exercise price, forfeitures and expirations in period (dollars per share) | $ / shares	53.40
Weighted average exercise price, ending (dollars per share) | $ / shares	43.54
Weighted average exercise price, exercisable (dollars per share) | $ / shares	$ 35.38
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 | $	$ 141
SSARs exercisable, Aggregate Intrinsic Value | $	$ 115