Inventories

3 Months Ended

Mar. 31, 2018

Inventory Disclosure [Abstract]

Inventories

13. Inventories

Costs included in inventories are raw materials, labor, supplies and allocable depreciation and overhead. Raw material inventories are valued on an average cost basis. Other inventory cost elements are valued at cost, using the first-in, first-out method. The Company writes down the inventories for estimated obsolescence, and to lower of cost or net realizable value based upon assumptions about future demand and market conditions. If actual demand or market conditions are less favorable than those projected by the Company, additional inventory write-downs may be required. Once established, the original cost of the inventory less the related write-down represents the new cost basis of such inventories. The decrease in Inventories in 2018, compared to the balances as of December 31, 2017, was principally due to the cumulative effect of adopting ASC 606 (see Note 2) which decreased Inventories by $47.1 million.

As of March 31, 2018 and December 31, 2017, inventories consisted of the following:

(in thousands)	March 31,  2018	December 31, 2017
Raw materials	$42,411	$42,215
Work in process	44,184	65,448
Finished goods	13,439	28,856
Total inventories	$100,034	$136,519