Inventories (Tables)

12 Months Ended

Dec. 31, 2018

Inventory Disclosure [Abstract]

Inventories

Inventories consisted of the following (in millions):

	2018		2017
Materials, spares and supplies	$	446	$	563
Work-in-process	2,161		1,823
Finished goods	390		492
Total inventories	$	2,997	$	2,878