Variable Interest Entities and Unconsolidated Investments (Unconsolidated Investements) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Loss from Unconsolidated Investments in Power Plants and Distributions [Line Items]
(Income) from unconsolidated subsidiaries	$ (24)	$ (22)	$ (24)
Distributions from Equity Method Investments	53	28	21
Greenfield [Member]
Income Loss from Unconsolidated Investments in Power Plants and Distributions [Line Items]
(Income) from unconsolidated subsidiaries	(11)	(14)	(10)
Distributions from Equity Method Investments	48	8	8
Whitby [Member]
Income Loss from Unconsolidated Investments in Power Plants and Distributions [Line Items]
(Income) from unconsolidated subsidiaries	(15)	(10)	(14)
Distributions from Equity Method Investments	5	20	13
Calpine Receivables [Member]
Income Loss from Unconsolidated Investments in Power Plants and Distributions [Line Items]
(Income) from unconsolidated subsidiaries	2	2	0
Distributions from Equity Method Investments	$ 0	$ 0	$ 0