Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted Cash and Cash Equivalents Items [Line Items]
Current	$ 167	$ 134
Non-current	34	25
Total	201	159
Basis Of Presentation and Summary of Significant Accounting Policies (Textuals) [Abstract]
Gain on Business Interruption Insurance Recovery	$ 14	27	$ 24
Income Taxes Threshold Percentage	50.00%
Property, plant and equipment, salvage value (as a percent)	10.00%
Goodwill	$ 242	242
Impairment losses	10	41	13
Asset retirement obligations	63	43
Long-term Debt	10,156	11,213
Property, Plant and Equipment, Net	$ 12,442	12,724
Jointly Owned Plants [Abstract]
Goodwill, Purchase Accounting Adjustments		6
Freestone Energy Center [Member]
Jointly Owned Plants [Abstract]
Jointly Owned Utility Plant, Proportionate Ownership Share	75.00%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 379
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	(167)
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	$ 1
Hidalgo Energy Center [Member]
Jointly Owned Plants [Abstract]
Jointly Owned Utility Plant, Proportionate Ownership Share	78.50%
Jointly Owned Utility Plant, Gross Ownership Amount of Plant in Service	$ 251
Jointly Owned Utility Plant, Ownership Amount of Plant Accumulated Depreciation	(114)
Jointly Owned Utility Plant, Ownership Amount of Construction Work in Progress	4
Debt Service
Restricted Cash and Cash Equivalents Items [Line Items]
Current	13	11
Non-current	8	8
Total	21	19
Construction Major Maintenance
Restricted Cash and Cash Equivalents Items [Line Items]
Current	23	28
Non-current	24	16
Total	47	44
Security Project Insurance
Restricted Cash and Cash Equivalents Items [Line Items]
Current	120	92
Non-current	0	0
Total	120	92
Other
Restricted Cash and Cash Equivalents Items [Line Items]
Current	11	3
Non-current	2	1
Total	$ 13	4
Greenfield [Member]
Basis Of Presentation and Summary of Significant Accounting Policies (Textuals) [Abstract]
Ownership percentage in equity method investment	50.00%
Whitby [Member]
Basis Of Presentation and Summary of Significant Accounting Policies (Textuals) [Abstract]
Ownership percentage in equity method investment	50.00%
Calpine Receivables [Member]
Basis Of Presentation and Summary of Significant Accounting Policies (Textuals) [Abstract]
Ownership percentage in equity method investment	100.00%
West [Member]
Basis Of Presentation and Summary of Significant Accounting Policies (Textuals) [Abstract]
Impairment losses	$ 0	28	13
Texas [Member]
Basis Of Presentation and Summary of Significant Accounting Policies (Textuals) [Abstract]
Impairment losses	0	13	0
East [Member]
Basis Of Presentation and Summary of Significant Accounting Policies (Textuals) [Abstract]
Impairment losses	10	0	$ 0
North American Power [Member]
Jointly Owned Plants [Abstract]
Goodwill, Acquired During Period		$ 49
Russell City Energy [Member]
Basis Of Presentation and Summary of Significant Accounting Policies (Textuals) [Abstract]
Long-term Debt	341
Property, Plant and Equipment, Net	676
Los Esteros Project [Member]
Basis Of Presentation and Summary of Significant Accounting Policies (Textuals) [Abstract]
Long-term Debt	163
Property, Plant and Equipment, Net	439
Minimum [Member]
Basis Of Presentation and Summary of Significant Accounting Policies (Textuals) [Abstract]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	180
Maximum [Member]
Basis Of Presentation and Summary of Significant Accounting Policies (Textuals) [Abstract]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification	$ 200