Capitalized Exploratory Well Costs and Undeveloped Leasehold Costs - Rollforward of Undeveloped Leasehold Costs (Details) $ in Millions	6 Months Ended
	Jun. 30, 2020 USD ($)
Proved Developed and Undeveloped Reserves
Undeveloped Leasehold Costs, Beginning of Period	$ 2,152
Additions to Undeveloped Leasehold Costs	2
Impairment	(1,488)
Other	(2)
Undeveloped Leasehold Costs, End of Period	$ 664