Investments in Affiliates (Schedule of Summarized Balance Sheet Information for Ibn Sina (National Methanol)) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Schedule of summarized balance sheet information for Ibn Sina (National Methanol) [Line Items]
Assets, Current	$ 3,807		$ 3,763
Current liabilities	$ 2,505		$ 1,973
National Methanol Company (Ibn Sina) [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of summarized balance sheet information for Ibn Sina (National Methanol) [Line Items]
Assets, Current		$ 283		$ 244
Assets, Noncurrent		806		817
Current liabilities		196		201
Liabilities, Noncurrent		$ 324		$ 372