Contingencies (Details) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Nov. 30, 2012 item	Sep. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) a
Environmental remediation
Number of potentially responsible parties (PRPs) | item	50
Number of industrial companies and governmental entities under review | item	30
Number of PRP groups discussing allocation proposals | item	2
Total site remediation costs expected to cover river bottom area in excess of amount spent to date				$ 342
Area of river bottom to be remediated (in acres) | a				200
Project costs to date				$ 100
Prior year collections of ICMS amounts realizable		$ 4	$ 56
Other Current Liabilities And Other Noncurrent Liabilities
Environmental remediation
Estimated potential liability for all environmental matters		$ 28		$ 28