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Optim Energy (Details) (USD $)
9 Months Ended
Sep. 30, 2011
Optim Energy [Member]
Dec. 31, 2012
Optim Energy [Member]
Sep. 23, 2011
Optim Energy [Member]
Sep. 22, 2011
Optim Energy [Member]
Jan. 04, 2012
Optim Energy [Member]
Schedule of Equity Method Investments [Line Items]          
Equity method investment,ownership percentage       50.00%  
PNMR equity investment in Optim Energy   $ 0      
Cost method investment, ownership percentage     1.00%    
Ownership percentage, sold         1.00%
Cost Method Investments         0
Equity Method Investment, Summarized Financial Information, Income Statement [Abstract]          
Operating revenues 256,800,000        
Gross margin 84,700,000        
Net earnings (loss) $ 21,400,000