Fair Value Measurements - Narrative (Details) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 $ / Mcfe $ / Barrel
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment and related charges, net of tax	$ 21			$ 156
Impairment and related charges		$ 8,600
Low end of range
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Operating and capital cost estimates, percentage					1.00%
Operating and capital cost estimates (in dollars per barrel) | $ / Barrel					50
High end of range
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Operating and capital cost estimates, percentage					2.00%
Operating and capital cost estimates (in dollars per barrel) | $ / Barrel					60
Crude Oil
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Sales price (dollars per barrel) | $ / Barrel					62.42
Unweighted arithmetic average price (in dollars per barrel) | $ / Barrel					59.17
Unweighted arithmetic average price, period					15 years
Crude Oil | Low end of range
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Sales price (dollars per barrel) | $ / Barrel					40
Crude Oil | High end of range
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Sales price (dollars per barrel) | $ / Barrel					70
Natural Gas
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unweighted arithmetic average price (in dollars per barrel) | $ / Mcfe					3.13
Unweighted arithmetic average price, period					15 years
Natural Gas | Low end of range
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Sales price (dollars per barrel) | $ / Mcfe					2.00
Natural Gas | High end of range
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Sales price (dollars per barrel) | $ / Mcfe					3.60
Gulf of Mexico
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment and related charges		1,200	$ 241
Algeria Oil and Gas Proved Properties
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment and related charges		900
Oman, Bolivia and the Gulf of Mexico
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment and related charges			293
Level 2 | Domestic Onshore Unproved Acreage
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment and related charges		$ 4,300
Level 3 | Measurement Input, Weighted Average Cost of Capital
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount rate		10.00%			10.00%
Ghana Assets | Discontinued Operations, Held-for-sale
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment and related charges, net of tax		$ 1,400
Impairment and related charges		2,200
Oil and gas segment
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impairment and related charges		$ 6,400	$ 581