Other Income and Expenses (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Other income:
Equity allowance for funds used during construction	$ 20	$ 29
Increase in cash surrender value of life insurance policies	7	7
Other	4	2
Total utility other income	31	38
Competitive power generation and other income	0	3
Total other income	31	41
Other expenses:
Civic, political and related activities and donations	6	7
Other	3	6
Total utility other expenses	9	13
Competitive power generation and other expenses	1	0
Total other expenses	$ 10	$ 13