Consolidated Statements of Operations (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Operating Revenues	$ 5,282	$ 5,197	$ 5,291
Operating Expenses
Fuel and purchased power	1,706	1,668	1,758
Operation and maintenance	1,331	1,376	1,429
Depreciation and amortization	927	896	822
Taxes other than income	267	260	256
Asset (gains) losses and impairments, net	(1)	(3)	(2)
Total operating expenses	4,230	4,197	4,263
Operating Income	1,052	1,000	1,028
Other (Income) and Deductions
Interest expense	250	268	272
Interest income	(1)	0	(1)
Other income	(62)	(54)	(53)
Other expenses	35	45	42
Total Other (Income) and Deductions	222	259	260
Income Before Income Taxes	830	741	768
Income Tax Expense	298	254	282
Net Income	$ 532	$ 487	$ 486