Concentration of Risk (Details)	12 Months Ended
Dec. 31, 2011	Dec. 31, 2011 Glencore Energy UK Ltd [Member]	Dec. 31, 2010 Glencore Energy UK Ltd [Member]	Dec. 31, 2011 Shell Trading (US) Company [Member]	Dec. 31, 2009 Suncor Energy Marketing [Member]
Concentration Risk [Line Items]
Percentage of crude oil sales (in hundredths)		24.00%	17.00%	17.00%	25.00%
Percentage of total oil, gas & NGL sales (in hundredths)		16.00%	11.00%	12.00%	16.00%
Concentration of credit risk [Abstract]
Short term deposits original maturities at time of purchase, description	three months or less
Accounts receivables, majority of accounts payment terms, description	30 days or less

Discloses the payment terms on accounts receivables due from customers or clients for goods or services sold.

No definition available.

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- Details

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- Definition

For an entity that discloses a concentration risk in relation to crude oil sales, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

No definition available.

+ Details

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- Definition

For an entity that discloses a concentration risk in relation to total oil and gas sales, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

No definition available.

+ Details

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- Details

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- Definition

Description of the characteristics of contracts treated as deposits for which assets are recorded as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 98-7

-Paragraph 18

+ Details

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