Acquisitions, Divestitures and Discontinued Operations (Details) (USD $)	3 Months Ended			6 Months Ended
	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 06, 2010	Jul. 02, 2010	Mar. 02, 2011 Conectiv
Summary of Conectiv Acquisition [Abstract]
Consideration							$ 1,640,000,000
Assets:
Current assets							78,000,000
Property, plant and equipment, net							1,574,000,000
Other long-term assets							85,000,000
Total assets acquired							1,737,000,000
Liabilities:
Current liabilities							46,000,000
Long-term liabilities							51,000,000
Total liabilities assumed							97,000,000
Net assets acquired							1,640,000,000
Components of Discontinued Operations
Operating revenues			25,000,000		50,000,000
Income from discontinued operations before taxes			12,000,000		20,000,000
Income tax expense			8,000,000		8,000,000
Discontinued operations, net of tax expense			4,000,000		12,000,000
Number of Conectiv power plants acquired							18
Cap on environmental remediation liabilities acquired							10,000,000
Number of Conectiv employees who joined Calpine							129
Proceeds from NDH Project Debt							1,300,000,000
Blue Spruce and Rocky Mountain ownership interest sold percentage						100.00%
Blue Spruce and Rocky Mountain sale price						739,000,000
Blue Spruce and Rocky Mountain gain on sale		209,000,000
Business Acquisition [Line Items]
Power generation capacity acquired (in Megawatts)	11,064	13,553		11,064				4,490
Calpine cash contribution				$ 52,000,000	$ 1,000,000