Summary of Significant Accounting Policies (Cash) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Cash and Cash Equivalents Items [Line Items]
Maximum maturity period of cash equivalent investments (in months)	3 months
Money market funds	$ 58	$ 107	$ 107
Cash reclassified to accounts payable	165		247
Southern California Edison
Cash and Cash Equivalents Items [Line Items]
Money market funds	5		5
Cash reclassified to accounts payable	$ 165		$ 242

- Definition

Investment in short-term money-market instruments (such as commercial paper, banker's acceptances, repurchase agreements, government securities, certificates of deposit, and so forth) which are highly liquid (that is, readily convertible to known amounts of cash) and so near their maturity that they present an insignificant risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify as cash equivalents by definition. Original maturity means an original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three-years ago does not become a cash equivalent when its remaining maturity is three months.

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