Document and Entity Information Cover - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Mar. 28, 2019	Jun. 30, 2018
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-K
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		105.2
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	Yes
Entity Current Reporting Status	No
Entity Public Float			$ 0