v3.20.1
Document and Entity Information - shares
3 Months Ended
Mar. 31, 2020
May 12, 2020
Entity Information [Line Items]    
Entity Registrant Name CALPINE CORP  
Entity Central Index Key 0000916457  
Current Fiscal Year End Date --12-31  
Entity Filer Category Non-accelerated Filer  
Document Type 10-Q  
Document Period End Date Mar. 31, 2020  
Document Fiscal Year Focus 2020  
Document Fiscal Period Focus Q1  
Amendment Flag false  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Current Reporting Status No  
Entity Common Stock, Shares Outstanding   105.2