Stock-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Apr. 30, 2023	Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2016
Estimated weighted average fair value for options granted and significant weighted average assumptions used [Abstract]
Weighted average fair value of options on grant date (in dollars per share)				$ 14.77
Options, Additional Disclosure [Abstract]
Options Outstanding, Number of Options (in shares)	312,000
Options Outstanding, Weighted Average Remaining Term (in years)	7 years 7 months 6 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 59.77
Options Exercisable, Number of Options (in shares)	103,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 60.49
$36.60 to $39.53
Options, Additional Disclosure [Abstract]
Weighted average grant date, fair value (in dollars per share)	36.60
Exercise price range, upper range limit (in dollars per share)	$ 39.53
Options Outstanding, Number of Options (in shares)	13,000
Options Outstanding, Weighted Average Remaining Term (in years)	7 years 8 months 12 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 37.26
Options Exercisable, Number of Options (in shares)	3,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 39.53
$45.99 to $53.79
Options, Additional Disclosure [Abstract]
Weighted average grant date, fair value (in dollars per share)	45.99
Exercise price range, upper range limit (in dollars per share)	$ 53.79
Options Outstanding, Number of Options (in shares)	40,000
Options Outstanding, Weighted Average Remaining Term (in years)	8 years 8 months 12 days
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 51.43
Options Exercisable, Number of Options (in shares)	3,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 53.24
$55.62 to $63.07
Options, Additional Disclosure [Abstract]
Weighted average grant date, fair value (in dollars per share)	55.62
Exercise price range, upper range limit (in dollars per share)	$ 63.07
Options Outstanding, Number of Options (in shares)	259,000
Options Outstanding, Weighted Average Remaining Term (in years)	7 years 6 months
Options Outstanding, Weighted Average Exercise Price (in dollars per share)	$ 62.17
Options Exercisable, Number of Options (in shares)	97,000
Options Exercisable, Weighted Average Exercise Price (in dollars per share)	$ 61.34
Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted (in shares)	20,000	300,000
Estimated weighted average fair value for options granted and significant weighted average assumptions used [Abstract]
Weighted average fair value of options on grant date (in dollars per share)	$ 9.24	$ 11.75
Weighted Average Assumptions [Abstract]
Expected life of options (years)	5 years 10 months 24 days	6 years 3 months 18 days
Risk-free interest rate	2.00%	1.20%
Expected volatility	32.40%	30.70%
Expected dividend yield	3.40%	2.40%
Fair value of common stock on grant date (in dollars per share)	$ 41.30	$ 56.51
Exercise price of stock option grant (in dollars per share)	$ 41.30	$ 61.84
Number of Options (in 000’s)
Outstanding at beginning of year (in shares)	310,000
Granted (in shares)	20,000	300,000
Exercised (in shares)	(14,000)
Expired or forfeited (in shares)	(4,000)
Outstanding at end of year (in shares)	312,000	310,000
Exercisable (in shares)	103,000
Vested and expected to vest in the future (in shares)	302,000
Weighted Average Exercise Price
Outstanding at beginning of year (in dollars per share)	$ 59.89
Granted (in dollars per share)	41.30
Exercised (in dollars per share)	39.53
Expired or forfeited (in dollars per share)	48.06
Outstanding at end of year (in dollars per share)	59.77	$ 59.89
Exercisable (in dollars per share)	60.49
Vested and expected to vest in the future (in dollars per share)	$ 60.18
Weighted Average Remaining Term (in years)
Outstanding at end of year	7 years 7 months 6 days
Exercisable at end of year	6 years 1 month 6 days
Vested and expected to vest in the future at end of year	7 years 7 months 6 days
Aggregate Intrinsic Value (in millions)
Outstanding at end of year	$ 0.0
Exercisable at end of year	0.0
Vested and expected to vest in the future	0.0
Options, Additional Disclosure [Abstract]
Award vesting amount	$ 1.7
Award vesting period	4 years
Weighted average recognition period for unrecognized share-based compensation	2 years 2 months 12 days
Options, exercises in period, intrinsic value	$ 0.1	$ 0.4	$ 0.2
Total grant date fair value of stock options vested	$ 0.5	$ 1.3
Options | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price of stock options granted as percentage of fair market value of stock at date of grant as required by the plan	100.00%
Options | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercisable period	10 years
Options | Share-based Payment Arrangement, Tranche One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	10.00%
Options | Share-based Payment Arrangement, Tranche Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	20.00%
Options | Share-Based Payment Arrangement, Tranche Three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	30.00%
Options | Share-based Compensation Award, Tranche Four
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage	40.00%
Executive Leadership Team
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted (in shares)	260,000
Grant price (in dollars per share)	$ 63.07
Number of Options (in 000’s)
Granted (in shares)	260,000
Other Leaders
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted (in shares)	40,000
Number of Options (in 000’s)
Granted (in shares)	40,000