Investments in Affiliates (Schedule of Summarized Income Statement Information for Ibn Sina (National Methanol)) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Schedule of Summarized Income Statement Financial Information for Ibn Sina (National Methanol) [Line Items]
Gross Profit	$ 1,293		$ 1,606		$ 1,972
Net earnings (loss)	$ 1,992		$ 858		$ 1,213
National Methanol Company (Ibn Sina) [Member] | Equity Method Investment, Nonconsolidated Investee or Group of Investees
Schedule of Summarized Income Statement Financial Information for Ibn Sina (National Methanol) [Line Items]
Revenues		$ 625		$ 726		$ 913
Gross Profit		187		299		396
Net earnings (loss)		$ 118		$ 227		$ 322