Consolidated Statements of Operations (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Statement [Abstract]
Operating Revenues	$ 5,152	$ 4,993	$ 4,714
Operating Expenses
Fuel and purchased power	1,716	1,580	1,491
Operation and maintenance	1,369	1,305	1,277
Depreciation and amortization	813	849	844
Taxes other than income	240	237	205
Asset (gains) and losses, net	12	(6)	(2)
Total operating expenses	4,150	3,965	3,815
Operating Income	1,002	1,028	899
Other (Income) and Deductions
Interest expense	289	313	325
Interest income	0	(1)	(2)
Other income	(47)	(39)	(39)
Other expenses	56	44	11
Total Other (Income) and Deductions	298	317	295
Income Before Income Taxes	704	711	604
Income Tax Expense	267	270	228
Net Income	$ 437	$ 441	$ 376