Inventories, net - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Inventory Disclosure [Abstract]
General and administrative costs included in work-in-process inventories	$ 509	$ 529
General and administrative costs incurred and recorded in inventories	3,500	3,300	$ 2,700
General and administrative costs charged to cost of sales from inventories	$ 3,500	$ 3,300	$ 2,800