Inventories (Tables)
 9 Months Ended
Sep. 30, 2016
Inventory Disclosure [Abstract]  
Inventories
($ in millions)
September 30, 2016
 
December 31, 2015
Finished products
$
1,063

 
$
1,055

Work in process
178

 
161

Raw materials
398

 
402

Supplies
37

 
41

Total Inventories
$
1,676

 
$
1,659