Inventory (Tables)

9 Months Ended

Sep. 30, 2017

Inventory Disclosure [Abstract]

Inventory Balance By Type

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

	September 30, 2017		December 31, 2016
Fuel and other raw materials	$	350	$	302
Spare parts and supplies	310		328
Total	$	660	$	630