Basis of Presentation and Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Pension and other postretirement non-service income	$ 18.9	$ 21.3	$ 54.9	$ 70.5
Cost of goods sold	3,701.1	3,270.4	10,967.1	9,618.5
Selling, general and administrative, excluding intangible amortization	$ 442.4	380.7	$ 1,287.4	1,157.3
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		21.3		70.5
Cost of goods sold		8.8		28.8
Selling, general and administrative, excluding intangible amortization		$ 12.5		41.7
ASU 2016-15 and 2016-18 [Member]
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Decrease in cash provided by operating activities				371.1
Increase in cash provided by investing activities				$ 365.2