Quarterly Consolidated Financial Data (unaudited) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Operating revenues	$ 1,939	$ 2,187	$ 1,939	$ 1,965	$ 1,438	$ 2,050	$ 1,572	$ 1,241	$ 8,030	$ 6,301	$ 5,478
Income (loss) from operations	390	1,126	329	144	151	597	122	4	1,989	874	1,002
Net income (loss) attributable to Calpine	$ 210	$ 614	$ 139	$ (17)	$ (97)	$ 306	$ (70)	$ (125)	$ 946	$ 14	$ 199
Net income (loss) per common share attributable to Calpine — basic (in dollars per share)	$ 0.55	$ 1.54	$ 0.33	$ (0.04)	$ (0.23)	$ 0.70	$ (0.16)	$ (0.28)	$ 2.34	$ 0.03	$ 0.43
Net income (loss) per common share attributable to Calpine — diluted (in dollars per share)	$ 0.54	$ 1.52	$ 0.33	$ (0.04)	$ (0.23)	$ 0.70	$ (0.16)	$ (0.28)	$ 2.31	$ 0.03	$ 0.42