Inventories
 6 Months Ended
Jun. 30, 2017
Inventory Disclosure [Abstract]  
Inventories
Inventories
($ in millions)
June 30, 2017
 
December 31, 2016
Finished products
$
1,114

 
$
947

Work in process
186

 
165

Raw materials
433

 
370

Supplies
33

 
32

Total Inventories
$
1,766

 
$
1,514


Most U.S. inventories are valued using the last-in, first-out method. These inventories represented approximately 35% and 38% of total inventories at June 30, 2017 and December 31, 2016, respectively. If the first-in, first-out method of inventory valuation had been used, inventories would have been $102 million and $106 million higher as of June 30, 2017 and December 31, 2016, respectively.