Document and Entity Information - shares
9 Months Ended
Sep. 30, 2017
Oct. 31, 2017
Document and Entity Information [Abstract]    
Document Type 10-Q  
Document Period End Date Sep. 30, 2017  
Document Fiscal Period Focus Q3  
Document Fiscal Year Focus 2017  
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   849,663,522