Reclassifications out of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income from operations before income taxes	$ (458)	$ (313)	$ (586)	$ (1,118)
Provision for income taxes	(141)	107	(216)	414
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of actuarial loss	(3)	(4)	(7)	(11)
Net settlement loss	(8)	(14)	(25)	(93)
Recognized gain on terminated derivative hedge	46	0	46	0
Ineffective portion of derivative hedge	0	0	1	0
Income from operations before income taxes	35	(18)	15	(104)
Provision for income taxes	(40)	6	(40)	38
Total reclassifications to expense, net of tax	(5)	(12)	(25)	(66)
Net recognized loss in discontinued operations, net of tax	0	0	(30)	0
Total reclassifications to expense	$ (5)	$ (12)	$ (55)	$ (66)