Derivative Instruments (Details 4) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on cash flow hedges before reclassification adjustment for cash flow hedges realized in net income (loss)		$ (2)	$ (6)	$ (48)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax		(40)	46	26
Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax	[1],[2]	(41)	45	21
Depreciation expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax	[1],[2]	1	1	5
Reclassification out of Accumulated Other Comprehensive Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on cash flow hedges before reclassification adjustment for cash flow hedges realized in net income (loss)		(2)	(6)	(48)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on cash flow hedges before reclassification adjustment for cash flow hedges realized in net income (loss)	[1],[2],[3],[4]	(1)	(5)	(43)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Depreciation expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on cash flow hedges before reclassification adjustment for cash flow hedges realized in net income (loss)	[1],[2],[3],[4]	$ (1)	$ (1)	$ (5)

[1] We recorded a gain of $1 million on hedge ineffectiveness related to our interest rate hedging instruments designated as cash flow hedges during the years ended December 31, 2018 and 2017. Upon the adoption of Accounting Standards Update 2017-12 on January 1, 2019, hedge ineffectiveness is no longer separately measured and recorded in earnings.

[2] We recorded an income tax benefit of $2 million and income tax expense of $5 million and $6 million for the years ended December 31, 2019, 2018 and 2017, respectively, 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 $72 million, $34 million and $72 million at December 31, 2019, 2018 and 2017, respectively. Cumulative cash flow hedge losses attributable to the noncontrolling interest, net of tax, remaining in AOCI were $3 million, $3 million and $6 million at December 31, 2019, 2018 and 2017, respectively.

[4] Includes losses of $2 million, $1 million and nil that were reclassified from AOCI to interest expense for the years ended December 31, 2019, 2018 and 2017, respectively, where the hedged transactions became probable of not occurring.