Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Feb. 14, 2019	Jun. 30, 2018
Document and Entity Information [Abstract]
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Period Focus	Q4
Document Fiscal Year Focus	2018
Amendment Flag	false
Entity Registrant Name	Marathon Oil Corp
Entity Central Index Key	0000101778
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Well Known Seasoned Issuer	Yes
Entity Common Stock, Shares Outstanding		818,504,459
Entity Public Float			$ 17,781