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	$ 152	$ 205	$ 584	$ 540
Items related to employee benefit plans:
Change in net actuarial loss, net of $(16), $(16), $(49) and $(46) tax	28	24	82	74
Change in net prior service costs, net of $(1), $(3), $(3) and $(8) tax	2	4	6	12
Foreign currency translation adjustment and other, net of $—, $—, $— and $— tax	(4)	(10)	(9)	(10)
Other comprehensive income	26	18	79	76
COMPREHENSIVE INCOME	$ 178	$ 223	$ 663	$ 616