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Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Additional Information (Details) (USD $)
 12 Months Ended
Dec. 31, 2012
contracts
Dec. 31, 2011
Dec. 31, 2010
Significant Accounting Policies [Line Items]      
Inventory provision for obsolescence $ 300,000 $ 200,000  
Capitalized internal costs 61,300,000 37,100,000 28,600,000
Liquidated restricted deposits 0 0 5,095,000
Restricted deposits 27,947,000 27,912,000  
Restricted deposit - pending sale 255,000,000 0  
Natural gas balancing liability 3,600,000 1,700,000  
Construction contracts using completed-contract method (in number of contracts) 2    
Advertising expense 11,800,000 4,800,000 5,400,000
Maximum
      
Significant Accounting Policies [Line Items]      
Maximum reserves sold from cost center not expected to result in significant alteration 25.00%    
Cholla Pipeline, L.P.
      
Significant Accounting Policies [Line Items]      
Noncontrolling interest ownership percentage 1.29% 1.29% 1.29%
Buildings | Maximum
      
Significant Accounting Policies [Line Items]      
Property, plant and equipment, useful life 39 years    
Buildings | Minimum
      
Significant Accounting Policies [Line Items]      
Property, plant and equipment, useful life 10 years    
Equipment | Maximum
      
Significant Accounting Policies [Line Items]      
Property, plant and equipment, useful life 30 years    
Equipment | Minimum
      
Significant Accounting Policies [Line Items]      
Property, plant and equipment, useful life 3 years    
Oil And Gas Unproved Properties
      
Significant Accounting Policies [Line Items]      
Interest capitalized during period 10,100,000 1,000,000 300,000
Midstream And Corporate Assets
      
Significant Accounting Policies [Line Items]      
Interest capitalized during period $ 4,700,000 $ 2,000,000 $ 1,000,000