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Inventory
6 Months Ended
Jun. 30, 2019
Inventory Disclosure [Abstract]  
INVENTORY INVENTORY
The following table summarizes the Company’s inventory balances as of the periods indicated (in millions):
 
June 30, 2019
 
December 31, 2018
Fuel and other raw materials
$
236

 
$
300

Spare parts and supplies
260

 
277

Total
$
496

 
$
577