Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements (Details)

v2.4.0.8
Fair Value Measurements (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Assets $ 324 $ 664  
Asset retirement obligation capitalized 3,556 2,195 1,390
Level 1 [Member] | Diamondback Energy LLC [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity investment in Diamondback 178,708 151,317  
Level 1 [Member] | Fixed Price Swaps [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Assets 0 0  
Liabilities 0 0  
Level 2 [Member] | Diamondback Energy LLC [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity investment in Diamondback 0 0  
Level 2 [Member] | Fixed Price Swaps [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Assets 845 664  
Liabilities 23,646 10,442  
Level 3 [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Asset retirement obligation capitalized 3,600    
Level 3 [Member] | Diamondback Energy LLC [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Equity investment in Diamondback 0 0  
Level 3 [Member] | Fixed Price Swaps [Member]
      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Assets 0 0  
Liabilities $ 0 $ 0