Accumulated Other Comprehensive Loss (Details 2) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Reclassifications out of accumulated other comprehensive income loss by component
INCOME BEFORE INCOME TAX EXPENSE	$ 249	$ 329	$ 946	$ 886
Income tax benefit	(97)	(124)	(362)	(346)
Net income	152	205	584	540
Amount reclassified from accumulated other comprehensive loss
Reclassifications out of accumulated other comprehensive income loss by component
Net actuarial loss	(44)	(40)	(131)	(120)
Prior service cost	(3)	(7)	(9)	(20)
INCOME BEFORE INCOME TAX EXPENSE	(47)	(47)	(140)	(140)
Income tax benefit	17	19	52	54
Net income	$ (30)	$ (28)	$ (88)	$ (86)