Inventory (Tables)

3 Months Ended

Mar. 31, 2017

Inventory Disclosure [Abstract]

Inventory Balance By Type

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

	March 31, 2017		December 31, 2016
Fuel and other raw materials	$	329	$	302
Spare parts and supplies	316		328
Total	$	645	$	630