Variable Interest Entities and Unconsolidated Investments (Unconsolidated VIEs) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Equity Method Investments Included on Balance Sheet [Abstract]
Equity Method Investments	$ 76	$ 106
Greenfield [Member]
Equity Method Investments Included on Balance Sheet [Abstract]
Equity Method Investments	$ 55	92
Equity Method Investment, Ownership Percentage	50.00%
Whitby [Member]
Equity Method Investments Included on Balance Sheet [Abstract]
Equity Method Investments	$ 15	6
Equity Method Investment, Ownership Percentage	50.00%
Calpine Receivables [Member]
Equity Method Investments Included on Balance Sheet [Abstract]
Equity Method Investments	$ 6	$ 8
Equity Method Investment, Ownership Percentage	100.00%