Commitments and Contingencies (Details) (USD $)	3 Months Ended			1 Months Ended	3 Months Ended					1 Months Ended
	Jun. 30, 2013	Sep. 30, 2013	Dec. 31, 2012	Oct. 31, 2012 Macondo well incident Plaintiff_Claim	Sep. 30, 2013 Macondo well incident bbl Independent_Bureaus Personal_Injury_Lawsuits Complaints Louisiana_Parishes Phases Decendents Allegedly_Injured_Persons Parties	Jun. 30, 2013 Macondo well incident	Dec. 15, 2010 Macondo well incident	Apr. 22, 2010 Macondo well incident Fatalities	Sep. 30, 2013 Securities and related litigation Class_Actions	Jan. 31, 2013 Transocean [Member] Macondo well incident Misdemeanor	Nov. 30, 2012 British Petroleum Exploration [Member] Macondo well incident Criminal_Charge Monitor
Loss Contingencies [Line Items]
Loss contingency related to Macondo well incident (non-current)		$ 1,022,000,000	$ 300,000,000
Loss contingency related to Macondo well (total)					1,300,000,000
Loss contingency related to Macondo well (current)					300,000,000
Federal government estimate of oil discharged from the well (in barrels)					4,900,000
Number of fatalities								11
Number of independent bureaus created to replace the Minerals Management Service					2
Number of parties-of-interest in the Marine Board investigation					16
Maximum per barrel civil penalty for strict liability under the CWA					1,100
Maximum per barrel civil penalty for gross negligence under the CWA					4,300
Liability cap under the OPA in addition to the full cost of removal of the discharged oil					75,000,000
Maximum civil penalty per violation under the ESA					25,000
Anadarko interest in Macondo well							25.00%
DOJ minimum estimate of removal costs and damages to the United States due to discharges of oil into the Gulf of Mexico					75,000,000
Loss Contingency Number Of Criminal Charges Plead Guilty											14
Loss Contingency Criminal Charges On Negligent Misinterpretation Of Negative Pressure Test Plead Guilty											13
Loss Contingency, Settlement Agreement, Consideration										1,000,000,000	4,000,000,000
Loss Contingency, Damages Paid, Value										400,000,000	1,300,000,000
Loss Contingency Drilling Probation Term						3 years					5 years
Loss Contingency Number Of Monitors											2
Loss Contingency Monitor Term											4 years
Number Of Misdemeanor Violations										1
Maximum per day fine for violating federal regulations related to INCs					35,000
Loss Contingency, Information about Litigation Matters [Abstract]
Minimum number of environmental class-action complaints					1,800
Criminal Fines, DOJ Macondo Settlement	200,000
Minimum number of wrongful death and personal injury multiple plaintiff lawsuits					8
Number of decedents in personal injury lawsuits					4
Number of allegedly injured persons in personal injury lawsuits					10
Minimum number of lawsuits naming the company					6
Number of Louisiana parishes included in pollution complaint					7
Number of phases involved in limitation action trial					2
Interest of MOEX in Macondo well (in hundreths)					10.00%
Number of similar class action lawsuits that were later consolidated into one suit									20
Number of Days to Pay Criminal Fine	5 days
Types Of Plaintiff Claims Dismissed				3
Indemnification and insurance [Abstract]
Total amount of general liability insurance program					600,000,000
Accrued Professional Fees					242,000,000
Legal fees and related expenses covered by insurance					211,000,000
Pre-tax charge recognized by BP as a result of the Macondo well incident					$ 40,000,000,000
Number Of Days To File Notice After Conclusion Of Mdl					15 days
Number Of Days To Appeal Incs Issued By Bsee					60 days