Schedule of Consolidated VIEs, Carrying Amounts of Assets and Liabilities (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020
Variable Interest Entity [Line Items]
Cash and cash equivalents and end of period	$ 2,911	$ 5,104	$ 4,549
Other current assets	962	889
Net property (variable interest entities restricted - 2021: $187; 2020: $232)	19,648	20,239
Deferred charges and other assets	1,426	1,249
Total Assets	61,749	61,470
Accrued and other current liabilities	3,701	3,790
Long-Term Debt (variable interest entities nonrecourse - 2021: $4; 2020: $6)	14,027	16,491
Other noncurrent obligations	6,424	6,279
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Cash and cash equivalents and end of period	49	26
Other current assets	38	44
Net property (variable interest entities restricted - 2021: $187; 2020: $232)	187	232
Deferred charges and other assets	15	17
Total Assets	289	319
Accrued and other current liabilities	51	73
Long-Term Debt (variable interest entities nonrecourse - 2021: $4; 2020: $6)	4	6
Other noncurrent obligations	14	18
Total Liabilities	$ 69	$ 97