Incentive Based Compensation Plans (Details 5-Performance)	3 Months Ended
Mar. 31, 2013
Performance Unit Disclosures [Abstract]
Performance Unit Granted	353,600
Performance Unit Awards Vesting Period	36 months

Performance units granted to executive officers upon achievement of certain goals. This is the number of units granted.

No definition available.

Name:	mro_AwardInstrumentsOtherThanOptionsPerformanceUnitGranted
Namespace Prefix:	mro_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration