|12 Months Ended|
Dec. 31, 2017
|Inventory Disclosure [Abstract]|
As of December 31, 2017 and 2016, inventory consisted of the following (in millions):
The entire disclosure for inventory. Includes, but is not limited to, the basis of stating inventory, the method of determining inventory cost, the classes of inventory, and the nature of the cost elements included in inventory.
Reference 1: http://www.xbrl.org/2003/role/presentationRef