Equity, Reclassification Out of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions		3 Months Ended												12 Months Ended
		Dec. 31, 2020	[1]	Sep. 30, 2020	[1],[2]	Jun. 30, 2020	[2]	Mar. 31, 2020	[2]	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Loss [Line Items]
Other income, net														$ 132		$ 104		$ 130
Total before tax														(2,010)		3,486		4,232
Tax benefit (expense)														903		(702)		(879)
Net income (loss)		$ (309)		$ (379)		$ 1,335		$ (1,754)		$ 1,330	$ 639	$ 648	$ 167	(1,107)		2,784		3,353
Revenues		$ 16,604		$ 15,809		$ 10,397		$ 22,102		$ 27,879	$ 27,249	$ 28,933	$ 24,263	64,912	[3]	108,324	[3]	117,033	[3]
Reclassification out of Accumulated Other Comprehensive Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Loss [Line Items]
Net income (loss)														(11)		(8)		(32)
Net Gain (Loss) on Pension and Other Postretirement Benefits [Member] | Reclassification out of Accumulated Other Comprehensive Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Loss [Line Items]
Total before tax														(53)		(14)		(41)
Tax benefit (expense)														12		4		9
Net income (loss)														(41)		(10)		(32)
Net Actuarial Loss [Member] | Reclassification out of Accumulated Other Comprehensive Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Loss [Line Items]
Other income, net	[4]													(74)		(38)		(63)
Prior Service Credit [Member] | Reclassification out of Accumulated Other Comprehensive Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Loss [Line Items]
Other income, net	[4]													26		28		29
Curtailment and Settlement [Member] | Reclassification out of Accumulated Other Comprehensive Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Loss [Line Items]
Other income, net	[4]													(5)		(4)		(7)
Gains on Cash Flow Hedges [Member[ | Reclassification out of Accumulated Other Comprehensive Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Loss [Line Items]
Total before tax														34		2
Tax benefit (expense)														(4)		0
Net income (loss)														30		2
Gains on Cash Flow Hedges [Member[ | Reclassification out of Accumulated Other Comprehensive Loss [Member] | Commodity Contracts [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Loss [Line Items]
Revenues														$ 34		$ 2
Gains on Cash Flow Hedges [Member[ | Reclassification out of Accumulated Other Comprehensive Loss [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Loss [Line Items]
Total before tax																		0
Tax benefit (expense)																		0
Net income (loss)																		0
Gains on Cash Flow Hedges [Member[ | Reclassification out of Accumulated Other Comprehensive Loss [Member] | Commodity Contracts [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Loss [Line Items]
Revenues																		$ 0

[1] We recorded a charge of $326 million in September 2020 due to the expected liquidation of LIFO inventory layers as described in Note 5. We recognized a benefit of $102 million in December 2020 to adjust the $326 million estimate to the $224 million actual charge for the year ended December 31, 2020.

[2] The market value of our inventories accounted for under the LIFO method fell below their historical cost on an aggregate basis as of March 31, 2020. As a result, we recorded an LCM inventory valuation adjustment of $2.5 billion in March 2020 as described in Note 5. The market value of our LIFO inventories improved due to the subsequent recovery in market prices, which resulted in a reversal of $2.2 billion in the quarter ended June 30, 2020 and the remaining amount in the quarter ended September 30, 2020.

[3] Includes excise taxes on sales by certain of our international operations of $4,797 million, $5,595 million, and $5,626 million for the years ended December 31, 2020, 2019, and 2018.

[4] These accumulated other comprehensive loss components are included in the computation of net periodic benefit cost, as discussed in Note 14.