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MATERIALS, SUPPLIES, AND INVENTORIES
 6 Months Ended
Jun. 30, 2017
Inventory Disclosure [Abstract]  
MATERIALS, SUPPLIES, AND INVENTORIES
MATERIALS, SUPPLIES, AND INVENTORIES

Our inventory consisted of:
(in millions)
 
June 30, 2017
 
December 31, 2016
Natural gas in storage
 
$
137.8

 
$
223.1

Materials and supplies
 
216.3

 
206.5

Fossil fuel
 
155.9

 
158.0

Total
 
$
510.0

 
$
587.6



PGL and NSG price natural gas storage injections at the calendar year average of the cost of natural gas supply purchased. Withdrawals from storage are priced using the LIFO cost method. For interim periods, the difference between current projected replacement cost and the LIFO cost for quantities of natural gas temporarily withdrawn from storage is recorded as a temporary LIFO liquidation debit or credit. The temporary LIFO liquidation amounts were not significant at June 30, 2017.

Substantially all other natural gas in storage, materials and supplies, and fossil fuel inventories are recorded using the weighted-average cost method of accounting.