Condensed Consolidated Statements of Income (Unaudited) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Condensed Consolidated Statements of Income [Abstract]
Operating revenues	$ 224	$ 213	$ 674	$ 637
Operating expenses
Operation and maintenance	84	81	242	235
Depreciation and amortization	51	53	148	148
Taxes, other than income taxes	6	14	41	41
Total operating expenses	141	148	431	424
Operating income	83	65	243	213
Earnings from unconsolidated affiliate	4	4	11	11
Other income, net	17	7	34	16
Interest and debt expense	(26)	(38)	(98)	(113)
Affiliated interest income, net	5	4	12	11
Income before income taxes	83	42	202	138
Income tax expense	33	14	77	51
Net income	$ 50	$ 28	$ 125	$ 87