Consolidated Statements of Operations (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating revenue	$ 4,882	$ 4,586	$ 4,432
Operating costs and expenses:
Energy costs	1,818	1,636	1,618
Operations and maintenance	1,242	1,103	1,081
Depreciation and amortization	640	611	561
Taxes, other than income taxes	161	152	136
Total operating costs and expenses	3,861	3,502	3,396
Operating income	1,021	1,084	1,036
Other income (expense):
Interest expense	(380)	(392)	(387)
Allowance for borrowed funds	29	25	45
Allowance for equity funds	58	47	79
Interest income	4	5	5
Other, net	2	(1)	(1)
Total other income (expense)	(287)	(316)	(259)
Income before income tax expense	734	768	777
Income tax expense	197	213	211
Net income	$ 537	$ 555	$ 566