Litigation, Claims and Contingencies - Summary of Components of Environmental Remediation Expense Included within Selling, General and Administrative Expense (Parenthetical) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Environmental Expense And Liabilities [Abstract]
Net expense relates to divested businesses	$ 2	$ 1	$ 2	$ 2