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Summary of Significant Accounting Policies Summary of Significant Accounting Policies - Additional Information (Details) (USD $)
 12 Months Ended
Dec. 31, 2013
contracts
Dec. 31, 2012
Dec. 31, 2011
Significant Accounting Policies [Line Items]      
Capitalized costs $ 1,335,416,000 $ 3,964,170,000 $ 1,774,303,000
Restricted deposit - pending sale 0 255,000,000  
Natural gas balancing liability 2,600,000 3,600,000  
Construction contracts using completed-contract method (in number of contracts) 2    
Advertising expense 5,100,000 11,800,000 4,800,000
Maximum
      
Significant Accounting Policies [Line Items]      
Maximum reserves sold from cost center not expected to result in significant alteration 25.00%    
Internal Costs
      
Significant Accounting Policies [Line Items]      
Capitalized costs 74,700,000 61,300,000 37,100,000
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 11,700,000 10,100,000 1,000,000
Midstream And Corporate Assets
      
Significant Accounting Policies [Line Items]      
Interest capitalized during period $ 4,900,000 $ 4,700,000 $ 2,000,000