Related Party Transactions (Details) (Southern California Edison, EME Natural Gas Fired Projects, USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2013 MW
Southern California Edison \| EME Natural Gas Fired Projects
Related Party Transaction [Line Items]
Term of power sales contract		10 years
Output		479
Expense for power purchased	$ 6	$ 6

The amount of purchased power charged against earnings for the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.2(b))

-URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688

Name:	us-gaap_UtilitiesOperatingExpensePurchasedPower
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration