Debt (Debt) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
Debt (Debt) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Aug. 10, 2020	Jun. 09, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Gain (Loss) on Extinguishment of Debt	$ (8)	$ (3)	$ (8)	$ 1
Subtotal	11,105		11,105				$ 11,706
Less: Current maturities	231		231				1,268
Total long-term debt	10,874		10,874				10,438
Repayments of Other Long-term Debt			412	$ 77
First Lien Term Loans
Debt Instrument [Line Items]
Subtotal	3,155		3,155				3,167
Senior Unsecured Notes
Debt Instrument [Line Items]
Subtotal	3,042		3,042				3,663
Senior Unsecured Notes
Debt Instrument [Line Items]
Gain (Loss) on Extinguishment of Debt	8
First Lien Notes
Debt Instrument [Line Items]
Subtotal	2,408		2,408				2,835
Project financing, notes payable and other
Debt Instrument [Line Items]
Subtotal	481		481				879
CCFC Term Loan
Debt Instrument [Line Items]
Subtotal	962		962				967
GPC Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount						$ 900
Subtotal	867		867				0
Line of Credit Facility, Maximum Borrowing Capacity						$ 200
Finance lease obligations
Debt Instrument [Line Items]
Subtotal	68		68				73
Revolving facilities
Debt Instrument [Line Items]
Subtotal	$ 122		$ 122				$ 122
Subsequent Event \| 2024 Senior Unsecured Notes(2)
Debt Instrument [Line Items]
Early Tender Offer Amount					$ 255
Subsequent Event \| 2029 Senior Unsecured Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					$ 650
Debt Instrument, Interest Rate, Stated Percentage					4.625%
Subsequent Event \| 2025 Senior Unsecured Notes(2)
Debt Instrument [Line Items]
Early Tender Offer Amount					$ 1,045
Subsequent Event \| 2031 Senior Unsecured Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount					$ 850
Debt Instrument, Interest Rate, Stated Percentage					5.00%
London Interbank Offered Rate (LIBOR) [Member] \| GPC Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	2.00%
Increase in GPC Loan Rate Every Three Years [Member] \| GPC Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.125%
Federal Funds Effective Rate [Member] \| GPC Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.50%
Prime Rate or The Eurodollar Rate For A One-Month Interest Period [Member] \| GPC Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.00%
Increase In LIBOR Plus Rate Every Three Years [Member] \| GPC Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.125%
Minimum [Member] \| GPC Term Loan [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						0.00%
Steamboat [Member]
Debt Instrument [Line Items]
Repayments of Other Long-term Debt	$ 342

CALPINE CORP 10-Q