Condensed Consolidated Statements of Income (Unaudited) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Condensed Consolidated Statements of Income [Abstract]
Operating revenues	$ 123	$ 126	$ 247	$ 271
Operating expenses
Operation and maintenance	50	47	96	91
Depreciation and amortization	18	22	41	43
Taxes, other than income taxes	7	8	15	16
Total operating expenses	75	77	152	150
Operating income	48	49	95	121
Other income, net	0	2	1	1
Interest and debt expense	(22)	(24)	(44)	(47)
Affiliated interest income, net	3	4	6	8
Income before income taxes	29	31	58	83
Income tax expense	11	12	22	32
Net income	$ 18	$ 19	$ 36	$ 51