v2.4.0.6
Capital Structure (Details) (USD $)
In Millions, except Share data, unless otherwise specified
 12 Months Ended 13 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Feb. 09, 2012
Feb. 07, 2012
Class of Stock [Line Items]          
Shares Of New, Reorganized Common Stock 485,000,000        
Common Stock, Shares Authorized 1,400,000,000 1,400,000,000      
Common Stock, Shares, Issued 490,468,815 444,883,356      
Common Stock, Par or Stated Value Per Share $ 0.001 $ 0.001      
Common Stock, Shares, Outstanding 481,743,738 444,435,198     481,743,738
Treasury Stock, Shares 8,725,077 448,158      
Treasury Stock, Value $ 125 $ 5      
Stock Repurchase Program, Authorized Amount 300        
Treasury Stock, Value, Acquired, Cost Method $ 120 $ 2 $ 2 $ 124  
Treasury Stock Acquired, Average Cost Per Share $ 14.60        
Common Stock Activity [Roll Forward]          
Total common shares outstanding, beginning balance 488,693,630 487,745,299 486,874,489 488,693,630  
Resolution of claims/inter-creditor disputes 0 0 0    
Shares issued under Calpine Equity Incentive Plans 1,187,181 948,331 870,810    
Share repurchase program 8,137,073     8,524,576  
Total common shares outstanding, ending balance 481,743,738 488,693,630 487,745,299    
Shares Issued [Member]
          
Common Stock Activity [Roll Forward]          
Total common shares outstanding, beginning balance 444,883,356 443,325,827 429,025,057 444,883,356  
Resolution of claims/inter-creditor disputes 44,258,432 488,612 13,167,420    
Shares issued under Calpine Equity Incentive Plans 1,327,027 1,068,917 1,133,350    
Share repurchase program 0        
Total common shares outstanding, ending balance 490,468,815 444,883,356 443,325,827    
Shares Held inTreasury [Member]
          
Common Stock Activity [Roll Forward]          
Total common shares outstanding, beginning balance 448,158 327,572 65,032 448,158  
Resolution of claims/inter-creditor disputes 0 0 0    
Shares issued under Calpine Equity Incentive Plans 139,846 120,586 262,540    
Share repurchase program 8,137,073        
Total common shares outstanding, ending balance 8,725,077 448,158 327,572    
Shares Held in Reserve [Member]
          
Common Stock Activity [Roll Forward]          
Total common shares outstanding, beginning balance 44,258,432 44,747,044 48,162,203 44,258,432  
Resolution of claims/inter-creditor disputes 44,258,432 488,612 3,415,159    
Shares issued under Calpine Equity Incentive Plans 0 0 0    
Share repurchase program 0        
Total common shares outstanding, ending balance 0 44,258,432 44,747,044    
Inter-Creditor Disputes [Member]
          
Common Stock Activity [Roll Forward]          
Total common shares outstanding, beginning balance 0 0 9,752,261 0  
Resolution of claims/inter-creditor disputes 0 0 9,752,261    
Shares issued under Calpine Equity Incentive Plans 0 0 0    
Share repurchase program 0        
Total common shares outstanding, ending balance 0 0 0