Consolidated Balance Sheets (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Current assets:
Cash and cash equivalents ($169 and $285 attributable to VIEs)	$ 587	$ 1,252
Accounts receivable, net of allowance of $14 and $13	532	598
Margin deposits and other prepaid expense	305	193
Restricted cash, current ($85 and $57 attributable to VIEs)	124	139
Derivative Assets, Current	1,049	1,051
Inventory and other current assets	337	329
Total current assets	2,934	3,562
Property, plant and equipment, net ($4,473 and $4,313 attributable to VIEs)	13,109	13,019
Restricted cash, net of current portion ($50 and $53 attributable to VIEs)	51	55
Investments	76	80
Derivative Assets, Noncurrent	158	113
Other assets	559	542
Total assets	16,887	17,371
Current liabilities:
Accounts payable	353	435
Accrued interest payable ($25 and $19 attributable to VIEs)	200	200
Debt, current portion ($39 and $41 attributable to VIEs)	103	104
Derivative liabilities, current	1,243	1,144
Other current liabilities	274	279
Total current liabilities	2,173	2,162
Debt, net of current portion ($2,731 and $2,522 attributable to VIEs)	10,488	10,321
Derivative Liabilities, Noncurrent	276	279
Other long-term liabilities	247	245
Total liabilities	13,184	13,007
Commitments and contingencies (see Note 10)
Stockholders’ equity:
Preferred stock, $0.001 par value per share; authorized 100,000,000 shares, none issued and outstanding	0	0
Common stock, $0.001 par value per share; authorized 1,400,000,000 shares, 492,024,794 and 490,468,815 shares issued, respectively, and 466,615,007 and 481,743,738 shares outstanding, respectively	1	1
Treasury stock, at cost, 25,409,787 and 8,725,077 shares, respectively	(420)	(125)
Additional paid-in capital	12,320	12,305
Accumulated deficit	(8,037)	(7,699)
Accumulated other comprehensive loss	(223)	(178)
Total Calpine stockholders’ equity	3,641	4,304
Noncontrolling interest	62	60
Total stockholders’ equity	3,703	4,364
Total liabilities and stockholders’ equity	16,887	17,371
Cash and Cash Equivalents At Carrying Value Attributable to VIE	169	285
Allowance for Doubtful Accounts Receivable, Current	14	13
Restricted Cash And Cash Equivalents At Carrying Value Attributable To VIE	85	57
Property Plant And Equipment Net Attributable To VIE	4,473	4,313
Restricted Cash And Cash Equivalents Noncurrent Attributable To VIE	50	53
Accrued Interest Attributable To VIE	25	19
Debt Current Attributable To VIE	39	41
Long Term Debt Noncurrent Attributable To VIE	$ 2,731	$ 2,522
Preferred Stock, Par or Stated Value Per Share	$ 0	$ 0
Preferred Stock, Shares Authorized	100	100
Preferred Stock, Shares Issued	0	0
Preferred Stock, Shares Outstanding	0	0
Common Stock, Par or Stated Value Per Share	$ 0	$ 0
Common Stock, Shares Authorized	1,400	1,400
Common Stock, Shares, Issued	492	490
Common Stock, Shares, Outstanding	467	482
Treasury Stock, Shares	25	9