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Summary of Significant Accounting Policies - Additional Information (Details) | 12 Months Ended
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Sep. 30, 2020 USD ($) Step | Sep. 30, 2019 USD ($) | Sep. 30, 2018 USD ($)
Accounting Policies [Abstract] |  |  |
Research and development costs charged to expense | $ 103,900,000 | $ 99,000,000.0 | $ 99,300,000
Advertising cost | 16,000,000.0 | 24,900,000 | 21,100,000
Amortization of Debt Issuance Costs | 3,600,000 | $ 1,600,000 | 5,600,000
Write off of Deferred Debt Issuance Cost | $ 1,800,000 |  | $ 3,200,000
Number of steps to evaluate uncertain income tax positions (in steps) | Step | 2 |  |
Minimum percentage likelihood of tax benefit being realized (as a percent) | 50.00% |  |
Maximum percentage likelihood of tax benefit being realized (as a percent) | 50.00% |  |
Amount of tax benefit realized for tax positions currently estimated to have a less than likelihood percentage of being sustained | $ 0 |  |
Maximum remaining maturity period at time of purchase of liquid investments classified as cash equivalents (in months) | 3 months |  |
Inventory valued using LIFO method (as a percent) | 83.00% | 84.00% |

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- Definition Represents the maximum percentage of the probability of individual tax position being sustained upon examination for not recognizing tax benefit. + References No definition available. + Details
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- Definition Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 720 -SubTopic 35 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6420018&loc=d3e36677-107848 + Details
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- Definition Amount of amortization expense attributable to debt issuance costs. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(8)) -URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399 + Details
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- Definition The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 985 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 730 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373 + Details
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