Acquisitions, Divestitures and Discontinued Operations (Textuals) (Details) $ in Millions		3 Months Ended		9 Months Ended	12 Months Ended
		Sep. 30, 2019 USD ($)	Mar. 31, 2017 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jul. 10, 2019 MW	Jan. 17, 2017 USD ($)
Business Acquisition [Line Items]
Dividends	[1]				$ 1,151	$ 20	$ 0
Impairment losses					84	10	41
(Gain) on sale of power plants, net					10	$ 0	27
North American Power [Member]
Business Acquisition [Line Items]
Ownership Percentage of Acquiree									100.00%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net									$ 105
Garrison Energy Center LLC [Member]
Business Acquisition [Line Items]
Power generation capacity | MW								309
RockGen Energy LLC [Member]
Business Acquisition [Line Items]
Power generation capacity | MW								503
Garrison Energy Center and RockGen Energy LLC [Member]
Business Acquisition [Line Items]
Ownership Percentage of Divestee								100.00%
Proceeds from Sale of Productive Assets		$ 360
Impairment losses					$ 55
Osprey Energy Center [Member]
Business Acquisition [Line Items]
Proceeds from Sale of Productive Assets			$ 166
(Gain) on sale of power plants, net							$ 27
Commodity Contract [Member]
Business Acquisition [Line Items]
Proceeds from Hedge, Financing Activities				$ 52
Dividend Paid [Member]
Business Acquisition [Line Items]
Dividends		$ 400

[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.