Annual report pursuant to Section 13 and 15(d)

Significant Accounting Policies (Percentage Of Revenue By Major Customers) (Details)

v2.4.0.6
Significant Accounting Policies (Percentage Of Revenue By Major Customers) (Details)
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Revenue, Major Customer [Line Items]      
Percentage of receipts 10.00%    
Shell Trading (US) Co. [Member]
     
Revenue, Major Customer [Line Items]      
Percentage of receipts 36.00% 40.00% 34.00%
ConocoPhillips [Member]
     
Revenue, Major Customer [Line Items]      
Percentage of receipts 16.00% 17.00%    [1]
J.P. Morgan Ventures Energy Corp. [Member]
     
Revenue, Major Customer [Line Items]      
Percentage of receipts 10.00%    [1] 15.00%
Chevron Corp. [Member]
     
Revenue, Major Customer [Line Items]      
Percentage of receipts    [1]    [1] 13.00%
[1] less than 10%