Revenue from Contracts with Customers Disaggregation of Revenues (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Revenue from Contract with Customer, Excluding Assessed Tax										$ 9,437		$ 9,865		$ 8,836
Revenues		$ 2,082	$ 2,792	$ 2,599	$ 2,599	$ 2,354	$ 2,890	$ 2,259	$ 2,009	10,072	[1]	9,512	[1]	8,752	[1]
Energy and Other Products [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										4,657		5,048
Capacity Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										845		903
Revenues Relating to Physical or Executory Contracts - Third Party [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										5,502		5,951
Affiliate Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]									0		0
Revenues Relating to Leases and Derivative Instruments [Member]
Revenues	[3]									4,570		3,561
West [Member]
Revenues	[1]									2,743		1,988		1,881
West [Member] | Energy and Other Products [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										948		1,070
West [Member] | Capacity Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										173		152
West [Member] | Revenues Relating to Physical or Executory Contracts - Third Party [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										1,121		1,222
West [Member] | Affiliate Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]									44		30
Texas [Member]
Revenues	[1]									3,081		2,860		2,342
Texas [Member] | Energy and Other Products [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										1,406		1,500
Texas [Member] | Capacity Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										125		94
Texas [Member] | Revenues Relating to Physical or Executory Contracts - Third Party [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										1,531		1,594
Texas [Member] | Affiliate Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]									55		34
East [Member]
Revenues	[1]									2,164		1,987		1,658
East [Member] | Energy and Other Products [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										609		621
East [Member] | Capacity Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										547		657
East [Member] | Revenues Relating to Physical or Executory Contracts - Third Party [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										1,156		1,278
East [Member] | Affiliate Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]									99		89
Retail [Member]
Revenues	[1]									4,093		3,976		$ 3,797
Retail [Member] | Energy and Other Products [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										1,694		1,857
Retail [Member] | Capacity Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										0		0
Retail [Member] | Revenues Relating to Physical or Executory Contracts - Third Party [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										1,694		1,857
Retail [Member] | Affiliate Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]									9		4
Intersegment Eliminations [Member] | Energy and Other Products [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										0		0
Intersegment Eliminations [Member] | Capacity Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										0		0
Intersegment Eliminations [Member] | Revenues Relating to Physical or Executory Contracts - Third Party [Member]
Revenue from Contract with Customer, Excluding Assessed Tax										0		0
Intersegment Eliminations [Member] | Affiliate Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	[2]									$ (207)		$ (157)

[1] Includes intersegment revenues of $530 million, $488 million and $324 million in the West, $946 million, $573 million and $361 million in Texas, $522 million, $234 million and $237 million in the East and $11 million, $4 million, $4 million in Retail for the years ended December 31, 2019, 2018 and 2017, 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.