Restructuring Charges (Changes to Restructuring Liability) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	$ 162	$ 87
Charge to Earnings	247	275	$ 173
Cash Paid	(265)	(172)
Non-Cash and Other	(48)	(28)
Restructuring reserve, ending balance	96	162	87
Employee termination costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	131	71
Charge to Earnings	155	185
Cash Paid	(202)	(125)
Non-Cash and Other	0	0
Restructuring reserve, ending balance	84	131	71
Asset impairment costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	0	0
Charge to Earnings	43	40
Cash Paid	0	0
Non-Cash and Other	(43)	(40)
Restructuring reserve, ending balance	0	0	0
Facility exit costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	2	2
Charge to Earnings	41	28
Cash Paid	(52)	(28)
Non-Cash and Other	0	0
Restructuring reserve, ending balance	(9)	2	2
Other exit costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, beginning balance	29	14
Charge to Earnings	8	22
Cash Paid	(11)	(19)
Non-Cash and Other	(5)	12
Restructuring reserve, ending balance	$ 21	$ 29	$ 14