Litigation (Details) $ in Millions							1 Months Ended		9 Months Ended	36 Months Ended
	Mar. 27, 2017 defendant LegalMatter	Jul. 22, 2016 USD ($)	Nov. 13, 2013 USD ($)	Jul. 02, 2013 USD ($)	Aug. 03, 2012 USD ($)	Feb. 14, 2011 USD ($)	Sep. 30, 2010 USD ($)	Aug. 31, 2010	Sep. 30, 2017 LegalMatter	Dec. 31, 1993 breach	Nov. 06, 2012	Jan. 03, 2012	Dec. 31, 2008 USD ($)	Dec. 31, 1998 USD ($)
Loss Contingencies [Line Items]
Number of contract breaches | breach										7
MTBE | Pending Litigation
Loss Contingencies [Line Items]
Pending lawsuits and claims (in number of claims) | LegalMatter									7
Ecuador
Loss Contingencies [Line Items]
Litigation settlement, amount awarded from		$ 96
Litigation settlement, amount, including interest		$ 113
Ecuador | Pending Litigation
Loss Contingencies [Line Items]
Conducted remediation program (in years)									3 years
Remediation program														$ 40
Financial compensation for purported damages on mining engineer's report													$ 18,900
Assessment for purported unjust enrichment on mining engineer's report													$ 8,400
Court order requiring the parties to provide their positions on damages within (in days)								45 days
Amount assessed in damages			$ 9,500			$ 8,600
Amount assessed for plaintiffs representatives						900
Additional amount assessed in punitive damages						$ 8,600
Public apology date within judgment/clarification ruling (in days)						15 days
Proposed additional payment for plaintiff attorney fees as percentage of judgment												0.10%
Litigation settlement, amount awarded to					$ 19,100
Percentage of payments withheld by third parties due to freeze order											40.00%
Percentage of funds withheld by banks due to freeze order											40.00%
Ecuador | Pending Litigation | Minimum
Loss Contingencies [Line Items]
Approximate damages on plaintiffs' submission							$ 16,000
Approximate unjust enrichment on plaintiffs' submission							5,000
Ecuador | Pending Litigation | Maximum
Loss Contingencies [Line Items]
Approximate damages on plaintiffs' submission							76,000
Approximate unjust enrichment on plaintiffs' submission							$ 38,000
Ecuador | Declaratory Relief Claim
Loss Contingencies [Line Items]
Pending lawsuits and claims (in number of claims) | LegalMatter									1
Writ of Certiorari
Loss Contingencies [Line Items]
Number of defendants | defendant	2
New claims filed, number | LegalMatter	1
Embargo Order | Ecuador
Loss Contingencies [Line Items]
Litigation settlement, amount awarded from				$ 96
Discovery Stay On Claims | Ecuador | Pending Litigation
Loss Contingencies [Line Items]
Pending lawsuits and claims (in number of claims) | LegalMatter									8