Inventory

3 Months Ended

Mar. 31, 2018

Inventory Disclosure [Abstract]

INVENTORY

INVENTORY

The following table summarizes the Company’s inventory balances as of the periods indicated (in millions):

	March 31, 2018		December 31, 2017
Fuel and other raw materials	$	281	$	284
Spare parts and supplies	288		278
Total	$	569	$	562