Consolidated Statements of Income (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011
Income Statement [Abstract]
Operating revenue	$ 2,412	$ 2,232
Fuel	77	76
Purchased power	615	508
Operation and maintenance	851	784
Depreciation, decommissioning and amortization	389	344
Property and other taxes	83	77
Total operating expenses	2,015	1,789
Operating income	397	443
Interest income	2	2
Other income	31	38
Interest expense	(121)	(111)
Other expenses	(9)	(13)
Income before income taxes	300	359
Income tax expense	99	123
Net income	201	236
Less: Dividends on preferred and preference stock	19	14
Net income available for common stock	$ 182	$ 222

The current period expense charged against earnings on long-lived, physical assets used in the normal conduct of business and not intended for resale to allocate or recognize the cost of assets over their useful lives; and to record the reduction in book value of an intangible asset over the benefit period of such asset; and to record the costs of decontaminating and decommissioning of facilities.

No definition available.