Inventories - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
General and administrative costs included in work-in-process inventories	$ 53	$ 112
General and administrative costs incurred and recorded in inventories	1,900	2,000	$ 1,900
General and administrative costs charged to cost of sales from inventories	2,000	2,000	$ 1,900
Capitalized contract cost	$ 443	$ 466