Other Income and Expenses (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Other income:
Equity allowance for funds used during construction	$ 27	$ 27	$ 47	$ 56
Increase in cash surrender value of life insurance policies	7	7	14	13
Other	2	5	6	8
Total utility other income	36	39	67	77
Competitive power generation and other income	2	3	1	6
Total other income	38	42	68	83
Other expenses:
Civic, political and related activities and donations	10	9	17	15
Other	9	4	9	10
Total utility other expenses	19	13	26	25
Competitive power generation and other expenses	0	0	0	0
Total other expenses	$ 19	$ 13	$ 26	$ 25