Revenue from Contracts with Customers Disaggregation of Revenues (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Revenue from Contract with Customer, Excluding Assessed Tax										$ 9,865		$ 8,836		$ 6,943
Revenues		$ 2,354	$ 2,890	$ 2,259	$ 2,009	$ 1,801	$ 2,586	$ 2,084	$ 2,281	9,512	[1]	8,752	[1]	6,716	[1]
Energy and Other Products [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										5,048
Capacity Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										903
Revenues Relating to Physical or Executory Contracts - Third Party [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										5,951
Affiliate Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]									0
Revenues Relating to Leases and Derivative Instruments [Member]
Revenues	[3]									3,561
West [Member]
Revenues	[1]									1,988		1,881		1,545
West [Member] | Energy and Other Products [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										1,070
West [Member] | Capacity Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										152
West [Member] | Revenues Relating to Physical or Executory Contracts - Third Party [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										1,222
West [Member] | Affiliate Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]									30
Texas [Member]
Revenues	[1]									2,860		2,342		2,145
Texas [Member] | Energy and Other Products [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										1,500
Texas [Member] | Capacity Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										94
Texas [Member] | Revenues Relating to Physical or Executory Contracts - Third Party [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										1,594
Texas [Member] | Affiliate Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]									34
East [Member]
Revenues	[1]									1,987		1,658		1,657
East [Member] | Energy and Other Products [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										621
East [Member] | Capacity Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										657
East [Member] | Revenues Relating to Physical or Executory Contracts - Third Party [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										1,278
East [Member] | Affiliate Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]									89
Retail [Member]
Revenues	[1]									3,976		$ 3,797		$ 1,520
Retail [Member] | Energy and Other Products [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										1,857
Retail [Member] | Capacity Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										0
Retail [Member] | Revenues Relating to Physical or Executory Contracts - Third Party [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										1,857
Retail [Member] | Affiliate Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]									4
Intersegment Eliminations [Member] | Energy and Other Products [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										0
Intersegment Eliminations [Member] | Capacity Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										0
Intersegment Eliminations [Member] | Revenues Relating to Physical or Executory Contracts - Third Party [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										0
Intersegment Eliminations [Member] | Affiliate Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]									$ (157)

[1] Includes intersegment revenues of $488 million, $324 million and $20 million in the West, $573 million, $361 million and $81 million in Texas, $234 million, $237 million and $48 million in the East and $4 million, $4 million, $2 million in Retail for the years ended December 31, 2018, 2017 and 2016, respectively.

[2] Affiliate energy, other and capacity revenues reflect revenues on transactions between wholesale and retail affiliates excluding affiliate activity related to leases and derivative instruments. All such activity supports retail supply needs from the wholesale business and/or allows for collateral margin netting efficiencies at Calpine.

[3] Revenues relating to contracts accounted for as leases and derivatives include energy and capacity revenues relating to PPAs that we are required to account for as operating leases and physical and financial commodity derivative contracts, primarily relating to power, natural gas and environmental products. Revenue related to derivative instruments includes revenue recorded in Commodity revenue and mark-to-market gain (loss) within our operating revenues on our Consolidated Statements of Operations.