Revenue Recognition - Summary of Effect of Adoption of ASC 606 Impact on Condensed Consolidated Statement of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation Of Revenue [Line Items]
Consolidated net income	$ 253.8	$ 271.3	$ 555.5	$ 1,629.3
Other assets			(171.7)	(119.9)
Inventories			(39.5)	(40.8)
Income taxes			(29.5)	$ 83.2
ASC 606 [Member] | Balances Without Adoption of ASC 606 [Member]
Disaggregation Of Revenue [Line Items]
Consolidated net income	253.2		553.8
Other assets			(174.5)
Inventories			(34.4)
Income taxes			(30.1)
ASC 606 [Member] | Impact of Adoption Increase/(Decrease) [Member]
Disaggregation Of Revenue [Line Items]
Consolidated net income	$ 0.6		1.7
Other assets			2.8
Inventories			(5.1)
Income taxes			$ 0.6