Derivative Instruments (Details 4) (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense		$ 159	$ 156	$ 471	$ 491
Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gains (Loss) Recognized in OCI (Effective Portion)	[1],[2]	(4)	11	4	2
Interest expense		1	7	2	9
Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Interest expense	[1],[2],[3],[4]	$ (12)	$ (8)	$ (36)	$ (34)

[1] We did not record any gain (loss) on hedge ineffectiveness related to our interest rate swaps designated as cash flow hedges during the three and nine months ended September 30, 2015 and 2014.

[2] We recorded an income tax expense of nil for each of the three and nine months ended September 30, 2015 and 2014, in AOCI related to our cash flow hedging activities.

[3] Cumulative cash flow hedge losses attributable to Calpine, net of tax, remaining in AOCI were $145 million and $149 million at September 30, 2015 and December 31, 2014, respectively. Cumulative cash flow hedge losses attributable to the noncontrolling interest, net of tax, remaining in AOCI were $12 million and $12 million at September 30, 2015 and December 31, 2014, respectively.

[4] Includes a loss of nil and $10 million for the three and nine months ended September 30, 2014, respectively, that was reclassified from AOCI to interest expense, where the hedged transactions are no longer expected to occur.