Capital Structure (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 08, 2018	Dec. 31, 2015
Class of Stock [Line Items]
Sale of Stock, Price Per Share				$ 15.25
Sale of Stock, Consideration Received on Transaction	$ 5,600
Common Stock, authorized shares (in shares)	5,000	1,400,000,000
Common Stock, issued shares (in shares)	105.2	361,677,891
Common Stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, outstanding shares (in shares)	105.2	360,516,091	359,061,764
Shares issued under Calpine Equity Incentive Plans	(121,906)
Stock Canceled During the Period, Shares	(360,394,185)
Stock Issued During Period, Shares, New Issues	105.2
Treasury Stock, Shares (in shares)	0	1,161,800
Treasury Stock, Value	$ 0	$ 15
Shares Issued [Member]
Class of Stock [Line Items]
Common Stock, issued shares (in shares)	105.2	361,677,891	359,627,113		356,755,747
Shares issued under Calpine Equity Incentive Plans	355,805	2,050,778	2,871,366
Stock Canceled During the Period, Shares	(362,033,696)
Stock Issued During Period, Shares, New Issues	105.2
Share repurchase program			0
Treasury Stock [Member]
Class of Stock [Line Items]
Shares issued under Calpine Equity Incentive Plans	(477,711)	(596,451)	(449,079)
Stock Canceled During the Period, Shares	1,639,511
Stock Issued During Period, Shares, New Issues	0
Share repurchase program			(22,527)
Treasury Stock, Shares (in shares)	0	1,161,800	565,349		93,743