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Represents the period over which shareholder return compares favorably to that of a competitor group of companies for purposes of calculating executive performance shares earned.

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Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of tax benefit for recognition of expense of award under share-based payment arrangement.

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Amount of tax benefit from exercise of option under share-based payment arrangement.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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Description of service or performance condition required to be met for earning right to award under share-based payment arrangement. Includes, but is not limited to, combination of market, performance or service condition.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Number of shares authorized for issuance under share-based payment arrangement.

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Stock-Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Oct. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award
Common stock reserved for issuance stock awards (in shares)		5,771,194
Income tax benefit recognized for stock-based compensation		$ 3.6	$ 4.9	$ 5.8
Stock options
Share-based Compensation Arrangement by Share-based Payment Award
Tenure of award (in years)		3 years
Share-based compensation arrangement by share-based payment award, vesting period		10 years
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value		$ 18.5	10.2	23.2
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options		4.3	$ 2.4	$ 6.3
Unrecognized compensation expense		$ 2.6
Weighted-average period for unrecognized compensation expense to be recognized (in years)		1 year 10 months 24 days
Weighted-average per share fair values for stock option granted (in dollars per share)		$ 26.16	$ 20.00	$ 26.84
Nonvested Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Unrecognized compensation expense		$ 8.4
Weighted-average period for unrecognized compensation expense to be recognized (in years)		1 year 10 months 24 days
Fair value of shares vested		$ 18.6	$ 12.3	$ 13.2
Income tax benefit recognized for stock-based compensation		$ 3.1	$ 2.1	$ 3.0
Weighted-average fair value, nonvested performance shares		$ 79.44	$ 72.66	$ 69.15	$ 55.22
Granted (in shares)		183,725	278,175	163,225
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Share-based compensation arrangement by share-based payment award, vesting period		3 years
Unrecognized compensation expense		$ 6.7
Weighted-average period for unrecognized compensation expense to be recognized (in years)		1 year 9 months 18 days
Share-based compensation arrangement by share-based payment award, vesting description		Performance share awards generally vest over a three-year service period following the grant date. Performance shares vest under two separate measurement criteria. The first type vest only if the Company’s total shareholder return (TSR) over the three year term of the awards compares favorably to that of a comparator group of companies. The second type vest only if the Company’s return on invested capital (ROIC) over the vesting period compares favorably to that of a comparator group of companies.
Performance Shares [Member] \| Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award
Stock Issued During Period, Shares, Share-based Compensation, Net of Forfeitures	68,125
Performance Shares [Member] \| Shareholder Return [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Weighted-average fair value, nonvested performance shares		$ 137.74	$ 85.89	$ 112.30
Nonvested Performance Share Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Fair value of shares vested		$ 6.9	$ 5.8	$ 7.6
Income tax benefit recognized for stock-based compensation		$ 0.2	$ 1.4	$ 2.1
Period over which shareholder return compares favorably to that of a competitor group of companies for purposes of calculating executive performance shares earned (in years)		3 years
Potential payouts, low end of range (as a percent)		0.00%
Potential payouts, high end of range (as a percent)		200.00%
Weighted-average fair value, nonvested performance shares		$ 89.54	$ 84.10	$ 89.11	$ 60.71
Granted (in shares)		55,325	73,950	57,625
Nonvested Performance Share Awards [Member] \| Shareholder Return [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percent		111.00%	126.00%	200.00%
Nonvested Performance Share Awards [Member] \| Return on Invested Capital [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percent		200.00%	200.00%	191.00%
Stock Appreciation Rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value		$ 0.7	$ 0.6	$ 3.8
Granted (in shares)		14,875	18,250	11,650
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award
Fair value of shares vested		$ 0.8	$ 0.4	$ 0.4
Granted (in shares)		7,925	8,350	8,125