Variable Interest Entities and Unconsolidated Investments (VIE Textuals) (Details) $ in Millions			3 Months Ended	12 Months Ended
		Jan. 01, 2020 USD ($)	Dec. 31, 2019 USD ($) yr MW	Dec. 31, 2019 USD ($) yr MW	Dec. 31, 2018 USD ($) MW	Dec. 31, 2017 USD ($)	Nov. 20, 2019
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of power plants and other	[1]			$ 322	$ 11	$ 162
Gain (Loss) on Disposition of Assets				10	0	$ 27
Equity Method Investment, Summarized Financial Information, Debt			$ 299	299	301
Prorata Share of Equity Method Investment, Summarized Financial Information, Debt			150	150	151
Long-term Debt			$ 11,857	11,857	$ 10,156
Put Option [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of power plants and other				280
Call Option [Member]
Schedule of Equity Method Investments [Line Items]
Proceeds from sale of power plants and other				$ 377
Russell City Energy [Member]
Schedule of Equity Method Investments [Line Items]
Minority Interest Ownership Percentage By Noncontrolling Third Party Owners			25.00%	25.00%
Equity Method Investment, Ownership Percentage			75.00%	75.00%
Variable Interest Entity, Primary Beneficiary [Member]
Schedule of Equity Method Investments [Line Items]
Power generation capacity | MW			6,669	6,669	7,880
Inland Empire Energy Center [Member]
Schedule of Equity Method Investments [Line Items]
Power generation capacity | MW			775	775
Put Option Exercise Period | yr			2,025	2,025
Minimum [Member] | Inland Empire Energy Center [Member]
Schedule of Equity Method Investments [Line Items]
Call Option Exercise Period | yr			2,017	2,017
Maximum [Member] | Inland Empire Energy Center [Member]
Schedule of Equity Method Investments [Line Items]
Call Option Exercise Period | yr			2,024	2,024
Calpine Receivables [Member]
Schedule of Equity Method Investments [Line Items]
Variable Interest Entity, Reporting Entity Involvement, Maximum Loss Exposure, Amount			$ 48	$ 48
Equity Method Investment, Ownership Percentage			100.00%	100.00%
Greenfield [Member]
Schedule of Equity Method Investments [Line Items]
Power generation capacity | MW			1,038	1,038
Equity Method Investment, Ownership Percentage	[2]		50.00%	50.00%
Whitby [Member]
Schedule of Equity Method Investments [Line Items]
Power generation capacity | MW			50	50
Equity Method Investment, Ownership Percentage	[3]		0.00%	0.00%
Equity Method Investment Ownership Interest Sold							50.00%
Gain (Loss) on Disposition of Assets			$ 5
OMEC [Member]
Schedule of Equity Method Investments [Line Items]
Long-term Debt	[4]		$ 0	$ 0	$ 218
Subsequent Event [Member] | Russell City Energy [Member]
Schedule of Equity Method Investments [Line Items]
Payments to Acquire Businesses, Net of Cash Acquired		$ 49

[1] Dividends paid during the years ended December 31, 2019 and 2018, includes approximately $1 million and $20 million, respectively, in certain Merger-related costs incurred by CPN Management, our parent.

[2] Includes our share of accumulated other comprehensive income/loss related to interest rate hedging instruments associated with our unconsolidated subsidiary Greenfield LP’s debt.

[3] On November 20, 2019, we sold our 50% interest in Whitby to a third party and recorded a gain on sale of assets, net of approximately $5 million.

[4] On August 14, 2019, we repaid the project debt associated with OMEC from a portion of the proceeds received from the issuance of our 2026 First Lien Term Loans (as discussed above), together with cash on hand.