Consolidated Statements of Changes in Equity (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012		Jun. 30, 2011
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, at the beginning of the period			$ 11,086		$ 11,494
Net income	103	191	215		405
Other comprehensive loss	(38)	(20)	(17)		(21)
Contributions from noncontrolling interests			238	[1]
Transfer of assets to Capistrano Wind Partners			(21)	[2]
Common stock dividends declared ($0.65 and $0.64 per share, 2012 and 2011 respectively)			(212)		(209)
Dividends, distributions to noncontrolling interests and other			(48)		(31)
Stock-based compensation and other			(41)		(13)
Noncash stock-based compensation and other			15		9
Issuance of preference stock			805		123
Redemption of preference stock			(75)
Balance, at the end of the period	11,945	11,757	11,945		11,757
Dividends declared per common share (in dollars per share)	$ 0.325	$ 0.320	$ 0.65		$ 0.64
Common Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, at the beginning of the period			2,360		2,331
Net income			0		0
Other comprehensive loss			0		0
Contributions from noncontrolling interests			0	[1]
Transfer of assets to Capistrano Wind Partners			(21)	[2]
Common stock dividends declared ($0.65 and $0.64 per share, 2012 and 2011 respectively)			0		0
Dividends, distributions to noncontrolling interests and other			0		0
Stock-based compensation and other			15		4
Noncash stock-based compensation and other			17		12
Issuance of preference stock			0		0
Redemption of preference stock			0
Balance, at the end of the period	2,371	2,347	2,371		2,347
Accumulated Other Comprehensive Income (Loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, at the beginning of the period			(139)		(76)
Net income			0		0
Other comprehensive loss			(17)		(21)
Contributions from noncontrolling interests			0	[1]
Transfer of assets to Capistrano Wind Partners			0	[2]
Common stock dividends declared ($0.65 and $0.64 per share, 2012 and 2011 respectively)			0		0
Dividends, distributions to noncontrolling interests and other			0		0
Stock-based compensation and other			0		0
Noncash stock-based compensation and other			0		0
Issuance of preference stock			0		0
Redemption of preference stock			0
Balance, at the end of the period	(156)	(97)	(156)		(97)
Retained Earnings
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, at the beginning of the period			7,834		8,328
Net income			167		376
Other comprehensive loss			0		0
Contributions from noncontrolling interests			0	[1]
Transfer of assets to Capistrano Wind Partners			0	[2]
Common stock dividends declared ($0.65 and $0.64 per share, 2012 and 2011 respectively)			(212)		(209)
Dividends, distributions to noncontrolling interests and other			0		0
Stock-based compensation and other			(56)		(17)
Noncash stock-based compensation and other			(2)		(2)
Issuance of preference stock			0		0
Redemption of preference stock			(1)
Balance, at the end of the period	7,730	8,476	7,730		8,476
Subtotal
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, at the beginning of the period			10,055		10,583
Net income			167		376
Other comprehensive loss			(17)		(21)
Contributions from noncontrolling interests			0	[1]
Transfer of assets to Capistrano Wind Partners			(21)	[2]
Common stock dividends declared ($0.65 and $0.64 per share, 2012 and 2011 respectively)			(212)		(209)
Dividends, distributions to noncontrolling interests and other			0		0
Stock-based compensation and other			(41)		(13)
Noncash stock-based compensation and other			15		10
Issuance of preference stock			0		0
Redemption of preference stock			(1)
Balance, at the end of the period	9,945	10,726	9,945		10,726
Other
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, at the beginning of the period			2		4
Net income			7		0
Other comprehensive loss			0		0
Contributions from noncontrolling interests			238	[1]
Transfer of assets to Capistrano Wind Partners			0	[2]
Common stock dividends declared ($0.65 and $0.64 per share, 2012 and 2011 respectively)			0		0
Dividends, distributions to noncontrolling interests and other			(7)		(2)
Stock-based compensation and other			0		0
Noncash stock-based compensation and other			0		0
Issuance of preference stock			0		0
Redemption of preference stock			0
Balance, at the end of the period	240	2	240		2
Preferred Stock and Preference Stock
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Balance, at the beginning of the period			1,029		907
Net income			41		29
Other comprehensive loss			0		0
Contributions from noncontrolling interests			0	[1]
Transfer of assets to Capistrano Wind Partners			0	[2]
Common stock dividends declared ($0.65 and $0.64 per share, 2012 and 2011 respectively)			0		0
Dividends, distributions to noncontrolling interests and other			(41)		(29)
Stock-based compensation and other			0		0
Noncash stock-based compensation and other			0		(1)
Issuance of preference stock			805		123
Redemption of preference stock			(74)
Balance, at the end of the period	$ 1,760	$ 1,029	$ 1,760		$ 1,029

[1] Funds contribution by third-party investors related to the Capistrano Wind equity capital raise are reported in noncontrolling interest. For further information, see Note 3.

[2] Common stock was reduced by $21 million during the six months ended June 30, 2012 due to a new tax basis in the assets transferred to Capistrano Wind Partners. The tax basis allocation to the transferred assets was updated during the three months ended June 30, 2012. For further information, see Note 3.