CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (Parenthetical) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Tax expense (benefit) of actuarial gains (losses)	$ 15	$ 25	$ 40	$ 75
Tax expense (benefit) of prior service credits (costs)	$ 0	$ (1)	$ 0	$ 0