Subsequent Events (Details) Boe in Thousands, $ in Millions		3 Months Ended			9 Months Ended
	Oct. 05, 2020 USD ($)	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($) Boe	Sep. 30, 2019 USD ($)	Oct. 31, 2020
Subsequent Event [Line Items]
Exploration expenses, including dry holes and lease impairment			$ 71	$ 50	$ 291	$ 127
Shenzi Field, Gulf of Mexico
Subsequent Event [Line Items]
Project interest percentage			28.00%		28.00%
Our net share of production (in barrels of oil equivalents per day) | Boe					11
Shenzi Field, Gulf of Mexico | Subsequent Event
Subsequent Event [Line Items]
Project interest percentage	28.00%
Consideration received from sale of working interest	$ 505
Galapagos Deep Well In Gulf Of Mexico
Subsequent Event [Line Items]
Exploration expenses, including dry holes and lease impairment			$ 37
Galapagos Deep Well In Gulf Of Mexico | Forecast
Subsequent Event [Line Items]
Exploration expenses, including dry holes and lease impairment		$ 7
Galapagos Deep Well In Gulf Of Mexico | Subsequent Event
Subsequent Event [Line Items]
Project interest percentage							25.00%