Condensed Consolidated Statements of Income and Comprehensive 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 and Comprehensive Income [Abstract]
Operating revenues	$ 92	$ 89	$ 308	$ 299
Operating expenses
Operation and maintenance	34	51	108	118
Depreciation and amortization	11	11	34	31
Taxes, other than income taxes	6	4	18	15
Total operating expenses	51	66	160	164
Operating income	41	23	148	135
Other income, net	1	2	2	6
Interest and debt expense, net	(15)	(15)	(46)	(44)
Affiliated interest income, net	1	0	1	1
Net income	28	10	105	98
Other comprehensive income
Unrealized actuarial gains on postretirement benefit obligations	9	0	9	0
Comprehensive income	$ 37	$ 10	$ 114	$ 98