Inventory (Tables)

12 Months Ended

Dec. 31, 2016

Inventory Disclosure [Abstract]

Inventory Balance By Type

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

December 31,	2016		2015
Fuel and other raw materials	$	302	$	343
Spare parts and supplies	328		328
Total	$	630	$	671