Commitments and Contingent Liabilities - Narrative (Details) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2020 USD ($)	Sep. 30, 2021 USD ($) site	Sep. 30, 2020 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Number of Superfund sites designated potentially responsible party at | site		14
Accrual for environmental loss contingencies, net of related receivables		$ 53.6	$ 59.2
Asset retirement obligation, net of recoveries		$ 23.6	$ 22.8
Gain (loss) related to litigation settlement	$ 70.0