Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Feb. 14, 2020	Jun. 30, 2019
Document and Entity Information [Abstract]
Title of 12(b) Security	Common Stock, par value $1.00
Entity Incorporation, State or Country Code	DE
Document Annual Report	true
Document Type	10-K
Document Period End Date	Dec. 31, 2019
Document Transition Report	false
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2019
Amendment Flag	false
Entity Registrant Name	Marathon Oil Corporation
Entity Central Index Key	0000101778
Entity Current Reporting Status	Yes
Entity Interactive Data Current	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		795,849,999
Entity Public Float			$ 11,398
Entity Address, Address Line One	5555 San Felipe Street,
Entity Address, City or Town	Houston,
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	77056-2723
City Area Code	(713)
Local Phone Number	629-6600
Entity Shell Company	false
Entity File Number	1-1513
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Tax Identification Number	25-0996816
Trading Symbol	MRO
Security Exchange Name	NYSE