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MATERIALS, SUPPLIES, AND INVENTORIES | 6 Months Ended
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Jun. 30, 2018
Inventory Disclosure [Abstract] |
MATERIALS, SUPPLIES, AND INVENTORIES | MATERIALS, SUPPLIES, AND INVENTORIES Our inventory consisted of:
(in millions) |  | June 30, 2018 |  | December 31, 2017
Natural gas in storage |  | $ | 121.9 |  |  | $ | 209.0 |
Materials and supplies |  | 221.4 |  |  | 211.2 |
Fossil fuel |  | 123.3 |  |  | 118.8 |
Total |  | $ | 466.6 |  |  | $ | 539.0 |
PGL and NSG price natural gas storage injections at the calendar year average of the costs of natural gas supply purchased. Withdrawals from storage are priced on 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the difference between current projected replacement cost and the LIFO cost for quantities of natural gas temporarily withdrawn from storage is recorded as a temporary LIFO liquidation debit or credit. At June 30, 2018, we had a temporary LIFO liquidation credit of $11.1 million recorded within other current liabilities on our balance sheet. Due to seasonality requirements, PGL and NSG expect these interim reductions in LIFO layers to be replenished by year end. Substantially all other natural gas in storage, materials and supplies, and fossil fuel inventories are recorded using the weighted-average cost method of accounting.

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- Definition The entire disclosure for inventory. Includes, but is not limited to, the basis of stating inventory, the method of determining inventory cost, the classes of inventory, and the nature of the cost elements included in inventory. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 330 -URI http://asc.fasb.org/topic&trid=2126998 + Details
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