CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) - 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]
Change in net actuarial loss, tax	$ 16	$ 2	$ 46	$ 6
Change in net prior service costs, tax	$ 3	$ 2	$ 8	$ 7