Basis of Presentation and Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Pension and other postretirement non-service income	$ 18.7	$ 24.6	$ 36.0	$ 49.2
Cost of goods sold	3,720.4	3,227.6	7,266.0	6,348.1
Selling, general and administrative, excluding intangible amortization	$ 444.1	395.8	$ 845.0	776.6
Accounting Standards Update 2017-07 \| Difference Between Guidance In Effect Before And After ASU201707 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Pension and other postretirement non-service income		24.6		49.2
Cost of goods sold		10.0		20.0
Selling, general and administrative, excluding intangible amortization		$ 14.6		29.2
ASU 2016-15 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Decrease in cash provided by operating activities				253.1
Increase in cash provided by investing activities				$ 253.1

The aggregate costs related to goods produced and sold and services rendered by an entity during the reporting period. This excludes costs incurred during the reporting period related to financial services rendered and other revenue generating activities.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc excluding amortization expense.

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