Inventories	3 Months Ended
Mar. 31, 2017
Inventory Disclosure [Abstract]
Inventories	5. Inventories Inventories are valued at the lower of cost or market for last-in, first-out (“LIFO”) inventory and lower of cost or net realizable value for first-in, first-out (“FIFO”) inventory. Approximately 40 percent of our inventories are valued using the LIFO method of determining cost. All other inventories are valued at the FIFO method of determining cost. An actual valuation of inventory under the LIFO method can be made only at the end of each year based on inventory levels and costs at that time. Accordingly, interim LIFO calculations must necessarily be based on management’s estimates of expected year-end inventory levels and costs. Because these are based on estimates, interim results, which were immaterial, are subject to change in the final year-end LIFO inventory valuation and therefore, no adjustment was recorded as of March 31, 2017, as consistent with prior interim reporting periods.

Inventories

3 Months Ended

Mar. 31, 2017

5. Inventories

Inventories are valued at the lower of cost or market for last-in, first-out (“LIFO”) inventory and lower of cost or net realizable value for first-in, first-out (“FIFO”) inventory. Approximately 40 percent of our inventories are valued using the LIFO method of determining cost. All other inventories are valued at the FIFO method of determining cost. An actual valuation of inventory under the LIFO method can be made only at the end of each year based on inventory levels and costs at that time. Accordingly, interim LIFO calculations must necessarily be based on management’s estimates of expected year-end inventory levels and costs. Because these are based on estimates, interim results, which were immaterial, are subject to change in the final year-end LIFO inventory valuation and therefore, no adjustment was recorded as of March 31, 2017, as consistent with prior interim reporting periods.