Document and Entity Information (USD $) In Millions, except Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Oct. 31, 2013	Jun. 29, 2012
Document and Entity Information [Abstract]
Document Type	10-Q
Document Period End Date	Sep. 30, 2013
Document Fiscal Period Focus	Q3
Document Fiscal Year Focus	2013
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		696,634,081
Entity Public Float			$ 17,991