Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement of Comprehensive Income [Abstract]
Net Income	$ 91	$ 79	$ 197	$ 207
Other Comprehensive Income
Losses on treasury rate locks reclassified into income	1		1
Pension and other postretirement benefit plans	2	2	7
Other comprehensive income, before income taxes	3	2	8
Income tax expense (benefit) related to other comprehensive income	2		3	(1)
Other comprehensive income, net of income taxes	1	2	5	1
Comprehensive Income	$ 92	$ 81	$ 202	$ 208