Supplemental Cash Flow Information (Details) - USD ($) $ in Millions			3 Months Ended	6 Months Ended		12 Months Ended
		Jan. 01, 2019	Mar. 31, 2020	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2020	Dec. 31, 2019		Dec. 31, 2018
Decrease (increase) in current assets:
Receivables, net						$ 2,773	$ (1,041)		$ (460)
Inventories						1,007	(385)		(197)
Prepaid expenses and other						101	0		(74)
Increase (decrease) in current liabilities:
Accounts payable						(4,068)	1,534		304
Accrued expenses						48	(27)		(113)
Taxes other than income taxes payable						37	60		(73)
Income taxes payable						(243)	153		(684)
Changes in current assets and current liabilities						(345)	294		(1,297)
Cash Flows Related to Interest and Income Taxes
Interest paid in excess of amount capitalized, including interest on finance leases						526	452		463
Income taxes paid (refunded), net (see Note 16)						203	(116)		1,361
Operating cash flows
Operating Leases						444	441
Finance Leases						97	50
Investing cash flows
Operating Leases						1	1
Financing cash flows
Finance Leases						80	40
Changes in lease balances resulting from new and modified leases, Operating Leases	[1]					263	1,756
Changes in lease balances resulting from new and modified leases, Finance Leases	[1]					950	239
Supplemental Cash Flow Information (Textual)
Decrease in receivables as a result of decreases in sales volumes and commodity prices						3,300
Increase in income taxes receivable						1,000
Construction in Progress [Member]
Supplemental Cash Flow Information (Textual)
MVP Terminal construction costs						2,399	1,731
Topic 842 [Member]
Financing cash flows
Changes in lease balances resulting from new and modified leases, Operating Leases		$ 1,300
MVP Terminal [Member]
Financing cash flows
Changes in lease balances resulting from new and modified leases, Finance Leases			$ 1,400			800
MVP Terminal [Member] | Magellan Midstream Partners LP (Magellan) [Member]
Supplemental Cash Flow Information (Textual)
Long-term liability recorded				$ 292					292
MVP Terminal [Member] | Construction in Progress [Member]
Supplemental Cash Flow Information (Textual)
MVP Terminal construction costs				539					539
MVP Terminal [Member] | Topic 842 [Member]
Supplemental Cash Flow Information (Textual)
Derecognized assets related to MVP		539
Derecognized liability related to MVP		292
Equity investment in MVP recorded due to derecognition of assets and liabilities		$ 247
2017 Tax Liabilities [Member]
Increase (decrease) in current liabilities:
Income taxes payable					$ (527)
2019 Tax Liabilities [Member]
Increase (decrease) in current liabilities:
Income taxes payable				$ (181)
U.S. [Member]
Cash Flows Related to Interest and Income Taxes
Income taxes paid (refunded), net (see Note 16)						130	(298)	[2]	$ 1,016
Internal Revenue Service (IRS) [Member] | U.S. [Member]
Supplemental Cash Flow Information (Textual)
Refund received, including interest, associated with income tax settlement							348
Blender's Tax Credit Receivable [Member]
Supplemental Cash Flow Information (Textual)
Receivable of (collection of) blender's tax credit receivable						$ (449)	$ 449

[1] Noncash activity for the year ended December 31, 2020 primarily included approximately $800 million for a finance lease ROU asset and related liability recognized in connection with the terminaling agreement with MVP described in Note 6. Noncash activity for the year ended December 31, 2019 included $1.3 billion for operating lease ROU assets and related liabilities recorded on January 1, 2019 upon adoption of Topic 842.

[2] This amount includes a refund of $348 million, including interest, that we received related to the settlement of the combined audit of our U.S. federal income tax returns for 2010 and 2011. See “Tax Returns Under Audit – U.S. Federal” on page 119.