Summary of Significant Accounting Policies (Narrative) (Details) - USD ($)	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Oct. 01, 2019	Apr. 01, 2019	Feb. 28, 2018
Finite-Lived Intangible Assets [Line Items]
Deferred gain/(loss) on hedging activity, net of tax	$ (9,200,000)	$ 15,000,000.0	$ 500,000
Available cash	258,500,000	522,100,000
Maximum amount authorized to sell	500,000,000.0
Receivables sold under program	300,200,000
Outstanding sold receivables	87,800,000
Receivables collected but not yet due	12,400,000
Fees associated with factoring	4,900,000
Amortization expense	9,100,000	7,400,000	5,300,000
Depreciation excluding accelerated	43,500,000	26,200,000	33,700,000
Accelerated depreciation	3,000,000.0
Advertising costs	96,700,000	80,100,000	$ 86,200,000
Accounting Standards Update 2018-15
Finite-Lived Intangible Assets [Line Items]
Capitalized implementation costs	800,000
Amortization expense on capitalized implementation costs	100,000
Scenario, Adjustment | Accounting Standards Update 2017-12 | Other items, net
Finite-Lived Intangible Assets [Line Items]
Deferred gain/(loss) on hedging activity, net of tax	(8,400,000)
Interest Rate Swap
Finite-Lived Intangible Assets [Line Items]
Variable rate debt hedged	200,000,000.0	$ 0
Interest rate on derivative instrument						2.47%
Notional value	$ 300,000,000.0				$ 50,000,000.0	$ 400,000,000.0
Minimum
Finite-Lived Intangible Assets [Line Items]
Amortization period, years	4 years
Minimum | Pro Forma | Accounting Standards Update 2016-02
Finite-Lived Intangible Assets [Line Items]
Right of use asset				$ 40,000,000
Operating lease liability				40,000,000
Minimum | Capitalized Software Costs
Finite-Lived Intangible Assets [Line Items]
Amortization period, years	3 years
Maximum
Finite-Lived Intangible Assets [Line Items]
Amortization period, years	15 years
Maximum | Pro Forma | Accounting Standards Update 2016-02
Finite-Lived Intangible Assets [Line Items]
Right of use asset				45,000,000
Operating lease liability				$ 45,000,000
Maximum | Capitalized Software Costs
Finite-Lived Intangible Assets [Line Items]
Amortization period, years	7 years
Machinery and Equipment | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated useful life, years	2 years
Machinery and Equipment | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated useful life, years	25 years
Building and Building Improvements | Minimum
Finite-Lived Intangible Assets [Line Items]
Estimated useful life, years	3 years
Building and Building Improvements | Maximum
Finite-Lived Intangible Assets [Line Items]
Estimated useful life, years	30 years
Restricted Stock Equivalents | Minimum
Finite-Lived Intangible Assets [Line Items]
Vesting period, in years	2 years
Restricted Stock Equivalents | Maximum
Finite-Lived Intangible Assets [Line Items]
Vesting period, in years	4 years
International | Cash
Finite-Lived Intangible Assets [Line Items]
Percentage of cash outside of the U.S.	75.80%	99.00%