Capitalized Exploratory Well Costs and Undeveloped Leasehold Costs - Rollforward of Undeveloped Leasehold Costs (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Proved Developed and Undeveloped Reserves [Roll Forward]
Undeveloped Leasehold Costs, Beginning of Period	$ 2,152
Additions to Undeveloped Leasehold Costs	2
Impairment (1)	(1,485)
Other	(2)
Undeveloped Leasehold Costs, End of Period	$ 667