Variable Interest Entities (Consolidated Projects or Entities) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended													0 Months Ended	1 Months Ended	3 Months Ended	0 Months Ended		12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2013 Variable Interest Entity, Primary Beneficiary MW projects	Dec. 31, 2012 Variable Interest Entity, Primary Beneficiary MW projects	Dec. 31, 2013 Additional Paid-in Capital [Member]	Dec. 31, 2012 Additional Paid-in Capital [Member]		Feb. 13, 2012 Cedro Hill Wind LLC [Member] MW	Feb. 13, 2012 Mountain Wind Power I [Member] MW	Feb. 13, 2012 Mountain Wind Power Il [Member] MW	Feb. 13, 2012 Capistrano Wind Partners [Member]	Jan. 31, 2013 Capistrano Wind Partners [Member]	Dec. 31, 2012 Capistrano Wind Partners [Member]	Feb. 13, 2012 Capistrano Wind Partners [Member] Mission Energy Holding Company	Feb. 13, 2012 Capistrano Wind Partners [Member] Mission Energy Holding Company	Dec. 31, 2013 Capistrano Wind Partners [Member] Third Party Investors	Jan. 31, 2013 Broken Bow I LLC [Member] MW	Dec. 31, 2012 Crofton Bluffs [Member] MW
Details of projects or entities
Number of projects consolidated (in projects)						16	15
Total generating capacity (in megawatts)						958	878
Summarized balance sheet information of VIEs
Current assets	$ 1,535		$ 1,323			$ 70	$ 74
Net property, plant and equipment	3,877		4,516			1,187	1,117
Other Assets, Miscellaneous, Noncurrent						112	90
Total Assets	6,973		7,520			1,369	1,281
Current liabilities	529		820			43	50
Long-term debt net of current portion	1,171		749			214	186
Deferred revenues	506		533			152	156
Long-term derivative liabilities	56		118			12	23
Other long-term liabilities	377		528			47	40
Total Liabilities	6,712		6,788			468	455
Noncontrolling interests	382		288			382	288
Assets serving as collateral for the debt obligations						609	497
Income (loss) from continuing operations before income taxes	(615)		(594)		(888)	10	29
Operating cash flows from continuing operations	233		(467)		660	59	75
Sale of ownership (in megawatts)											150	61	80							80	40
Variable Interest Entities, Sales Price																				112	58
Class A equity ownership percentage (as a percent)																	100.00%
Preferred equity interests to receive percent of cash available for distribution (as a percent)														100.00%
Cash available for distribution includes percent of tax benefits to be realized (as a percent)														90.00%
Contributions from noncontrolling interests	94	[1]	288	[1]				0	0					238	94	46		4	378
Transfers of assets to Capistrano Wind Partners			$ 21	[2]					$ 21	[2]

[1] Funds contributed by third-party investors to Capistrano Wind Partners. For further information, see Note 3—Variable Interest Entities—Projects or Entities that are Consolidated—Capistrano Wind Partners.

[2] Additional paid in capital was reduced by $21 million due to a new tax basis in the assets transferred to Capistrano Wind Partners. For further information, see Note 3—Variable Interest Entities—Projects or Entities that are Consolidated—Capistrano Wind Partners.