Restructuring Charges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restructuring Charges
Beginning Balance	$ 261	$ 470	$ 233
Restructuring charges, net of revisions	329	(26)	411
Payments	(192)	(155)	(115)
Other non-cash	(15)	(28)	(59)
Ending Balance	383	261	470
Employee Severance [Member]
Restructuring Charges
Beginning Balance	238	435	196
Restructuring charges, net of revisions	305	(33)	383
Payments	(171)	(141)	(93)
Other non-cash	(12)	(23)	(51)
Ending Balance	360	238	435
Other Terminations [Member]
Restructuring Charges
Beginning Balance	23	35	37
Restructuring charges, net of revisions	24	7	28
Payments	(21)	(14)	(22)
Other non-cash	(3)	(5)	(8)
Ending Balance	$ 23	23	$ 35
GBT JV [Member]
Restructuring Charges
Other non-cash		(42)
Foreign exchange and other non-cash charges
Restructuring Charges
Other non-cash		$ (17)