Litigation (Details) (Pending Litigation [Member], USD $)	0 Months Ended	1 Months Ended		3 Months Ended
	Aug. 03, 2012	Sep. 30, 2010	Aug. 31, 2010	Mar. 31, 2013 LegalMatter	Nov. 06, 2012	Jan. 03, 2012	Feb. 14, 2011	Dec. 31, 2008
MTBE [Member]
Loss Contingencies [Line Items]
Pending lawsuits and claims (in number of claims)				6
Ecuador [Member]
Loss Contingencies [Line Items]
Pending lawsuits and claims (in number of claims)				9
Conducted remediation program (in years)				3 years
Remediation program				$ 40,000,000
Financial compensation for purported damages on mining engineer's report								18,900,000,000
Assessment for purported unjust enrichment on mining engineer's report								8,400,000,000
Court order requiring the parties to provide their positions on damages within (in days)			45 days
Approximate damages on plaintiffs' submission, Minimum		16,000,000,000
Approximate damages on plaintiffs' submission, Maximum		76,000,000,000
Approximate unjust enrichment on plaintiffs' submission, Minimum		5,000,000,000
Approximate unjust enrichment on plaintiffs' submission, Maximum		38,000,000,000
Amount assessed in damages							8,600,000,000
Amount assessed for plaintiffs representatives							900,000,000
Additional amount assessed in punitive damages							8,600,000,000
Public apology date within judgment/clarification ruling (in days)							15 days
Proposed additional payment for plaintiff attorney fees as percentage of judgment						0.10%
Approved court-appointed liquadator's report damanges for total judgment	$ 19,100,000,000
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 [Member] | Declatory Relief Claim [Member]
Loss Contingencies [Line Items]
Pending lawsuits and claims (in number of claims)				1
Ecuador [Member] | Discovery Stay On Claims [Member]
Loss Contingencies [Line Items]
Pending lawsuits and claims (in number of claims)				8