Inventories - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Inventory, Net [Abstract]
Inventory valuation reserves	$ 430	$ 360
Inventory, Net, Items Net of Reserve Alternative [Abstract]
Finished goods	2,575	2,577
Work in process and raw materials	2,045	1,930
Total inventories, net	4,620	4,507
Inventory Impairment	$ 105	$ 157