Consolidated Statements Of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 460	$ 452	$ 1,252	$ 1,195
Other comprehensive income, before tax:
Pension and other postretirement benefits	7	10	20	31
Other comprehensive loss of equity investees	0	0	0	(4)
Other comprehensive income, before tax	7	10	20	27
Income tax expense related to items of other comprehensive income	(3)	(3)	(8)	(11)
Other comprehensive income, net of tax	4	7	12	16
Total comprehensive income	$ 464	$ 459	$ 1,264	$ 1,211