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Inventory (Notes)
12 Months Ended
Dec. 31, 2016
Inventory Disclosure [Abstract]  
Inventory
Inventory
Inventory consisted of:
 
As of December 31,
 
2016
 
2015
 
(In millions)
Fuel oil
$
289

 
$
312

Coal/Lignite
334

 
471

Natural gas
28

 
12

Spare parts
413

 
437

Other
47

 
20

Total Inventory
$
1,111


$
1,252


During the year ended December 31, 2015, the Company recorded a lower of weighted average cost or market adjustment related to fuel oil of $19 million.