Consolidated Statements of Income (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Income Statement [Abstract]
Operating revenue	$ 3,731	$ 3,386	$ 8,794	$ 8,063
Fuel	82	110	220	269
Purchased power	1,612	1,264	3,049	2,422
Operation and maintenance	906	819	2,622	2,450
Depreciation, decommissioning and amortization	399	358	1,187	1,058
Property and other taxes	73	71	229	217
Total operating expenses	3,072	2,622	7,307	6,416
Operating income	659	764	1,487	1,647
Interest income	2	2	5	7
Other income	36	26	103	103
Interest expense	(124)	(116)	(373)	(344)
Other expenses	(9)	(10)	(36)	(35)
Income before income taxes	564	666	1,186	1,378
Income tax expense	176	245	384	496
Net income	388	421	802	882
Less: Dividends on preferred and preference stock	25	15	66	44
Net income available for common stock	$ 363	$ 406	$ 736	$ 838

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.