Share-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Compensation Related Costs [Abstract]
Number of shares initially registered and authorized for issuance	15,385,436
Total number of shares outstanding (in shares)	2,417,467
Number of shares issued (in shares)	10,902,249
Number of shares available for future issuance (in shares)	2,049,615
Stock-based compensation cost	$ 17.9	$ 20.3	$ 22.2
Less impact of income tax	4.2	4.7	5.1
Stock-based compensation cost, net of tax	13.7	15.6	17.1
Current tax benefit realized from the exercise of stock options and payment of restricted stock units	$ 2.3	$ 3.2	$ 6.4
Number of shares
Granted (in shares)	0	0	0
Weighted average exercise price
Share-Based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount	$ 0.0
Time Based Stock Awards
Assumptions used in the determination of fair value of options
Expected life	2 years 9 months 29 days	2 years 9 months 29 days	2 years 9 months 29 days
Risk-free interest rate (as a percent)	4.06%	4.28%	3.96%
Weighted-average dividend yield (as a percent)	0.00%	0.00%	0.00%
Actual dividend rate (as a percent)	2.24%	1.95%	1.97%
Weighted-average volatility factor (as a percent)	36.00%	32.40%	44.70%
Weighted average exercise price
Unrecognized stock-based compensation	$ 11.2
Period for recognition of unrecognized stock-based compensation	1 year 10 months 24 days
Number of shares
Number of shares outstanding under time-based stock awards and performance-based stock awards at the beginning of the period (in shares)	546,688	498,736
Granted (in shares)	496,662	360,823
Vested (in shares)	(294,884)	(260,712)
Forfeited (in shares)	(124,037)	(52,159)
Number of shares outstanding under time-based stock awards and performance-based stock awards at the end of the period (in shares)	624,429	546,688	498,736
Weighted-Average Grant Date Fair Value
Non-vested time-based stock awards at the beginning of the period (in dollars per share)	$ 43.09	$ 46.91
Granted (in dollars per share)	31.76	39.76
Vested (in dollars per share)	44.13	45.51
Forfeited (in dollars per share)	34.88	44.51
Non-vested time-based stock awards at the end of the period (in dollars per share)	$ 35.22	$ 43.09	$ 46.91
Aggregate fair value	$ 16.9
Time Based Stock Awards and Performance Based Stock Awards
Time-based stock awards and performance-based stock awards
Total vest date fair value of vested time-based stock awards and performance-based stock awards shares held by employees and directors	$ 12.9	$ 15.6	$ 28.0
Weighted-Average Grant Date Fair Value
Number of shares under the time-based and performance-based stock awards due to dividend reinvestment (in shares)	54,462
Aggregate fair value of shares under the time-based and performance-based stock awards plans due to dividend reinvestment	$ 1.5
Vested Deferred Stock
Vested deferred stock (in shares)	370,657
Aggregate fair value of vested deferred stock	$ 10.0
Employee Stock Option
Share-based compensation
Vesting period		3 years
Number of shares
Outstanding at the beginning of the period (in shares)	553,891	627,609
Granted (in shares)	0	0
Exercised (in shares)	(31,163)	(68,140)
Forfeited (in shares)	0	0
Expired (in shares)	(6,946)	(5,578)
Outstanding at the end of the period (in shares)	515,782	553,891	627,609
Exercisable at the end of the period (in shares)	515,782
Weighted average exercise price
Outstanding at the beginning of the period (in dollars per share)	$ 38.91	$ 38.56
Granted (in dollars per share)	0	0
Exercised (in dollars per share)	32.16	35.85
Forfeited (in dollars per share)	0	0
Expired (in dollars per share)	33.58	37.15
Outstanding at the end of the period (in dollars per share)	39.39	$ 38.91	$ 38.56
Exercisable at the end of the period (in dollars per share)	$ 39.39
Average remaining life of outstanding stock options	2 years 4 months 24 days
Aggregate intrinsic value of outstanding options	$ 0.0
Total intrinsic value of options exercised	0.1	$ 0.7	$ 9.2
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares	0.0	$ 0.0	$ 2.2
Performance Shares
Weighted average exercise price
Unrecognized stock-based compensation	$ 8.0
Period for recognition of unrecognized stock-based compensation	1 year 8 months 12 days
Number of shares
Number of shares outstanding under time-based stock awards and performance-based stock awards at the beginning of the period (in shares)	758,060	582,476
Granted (in shares)	611,670	482,914
Vested (in shares)	(16,105)	(48,268)
Forfeited (in shares)	(446,995)	(259,062)
Number of shares outstanding under time-based stock awards and performance-based stock awards at the end of the period (in shares)	906,630	758,060	582,476
Weighted-Average Grant Date Fair Value
Non-vested time-based stock awards at the beginning of the period (in dollars per share)	$ 51.54	$ 59.90
Granted (in dollars per share)	40.04	42.18
Vested (in dollars per share)	51.61	46.18
Forfeited (in dollars per share)	58.01	53.90
Non-vested time-based stock awards at the end of the period (in dollars per share)	$ 40.57	$ 51.54	$ 59.90
Aggregate fair value	$ 15.9
Vested Deferred Stock
Performance measurement period used to determined shares granted included in performance-based stock awards	3 years
Performance Shares, SV
Share-based compensation
Vesting period	3 years
Performance Shares, TSR
Share-based compensation
Vesting period	3 years
Vested Deferred Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Below 25th Percentile, Payout Percent	0.00%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, At 25th Percentile, Payout Percent	25.00%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, At 50th Percentile, Payout Percent	100.00%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, At 75th Percentile And Above, Payout Percent	200.00%