XML 54 R34.htm IDEA: XBRL DOCUMENT v2.4.0.6
Fair Value Measurements (Hierarchy Of Fair Value, Assets And Liabilities Measured On Recurring Basis) (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2012
Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets (liabilities) $ 178,207 $ 245,369
Commodity Derivative Instruments [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets (liabilities) (22,345) (5,050)
Money Market Funds [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets (liabilities) 200,552 250,419
Fair Value, Inputs, Level 1 [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets (liabilities) 200,552 250,419
Fair Value, Inputs, Level 1 [Member] | Commodity Derivative Instruments [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets (liabilities)      
Fair Value, Inputs, Level 1 [Member] | Money Market Funds [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets (liabilities) 200,552 250,419
Fair Value, Inputs, Level 2 [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets (liabilities) (22,345)   
Fair Value, Inputs, Level 2 [Member] | Commodity Derivative Instruments [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets (liabilities) (22,345)   
Fair Value, Inputs, Level 2 [Member] | Money Market Funds [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets (liabilities)     
Fair Value, Inputs, Level 3 [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets (liabilities)   (5,050)
Fair Value, Inputs, Level 3 [Member] | Commodity Derivative Instruments [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets (liabilities)   (5,050)
Fair Value, Inputs, Level 3 [Member] | Money Market Funds [Member]
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets (liabilities)