Accounts Receivable and Inventories (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accounts Receivable, Net, Current [Abstract]
Trade accounts receivable	$ 280,526	$ 340,223
Less: Allowance for doubtful accounts	(25,649)	(15,119)
Trade accounts receivable, net	254,877	325,104
Other receivables	30,395	28,145
Provision for doubtful accounts related to trae accounts receivable	13,047	9,892	$ 10,175
Inventories
Finished goods	32,586	30,525
Work-in-process	86,745	28,690
Raw materials and purchased parts	70,755	87,985
Stores and supplies	26,881	31,722
Total inventories	216,967	178,922
Valued at lower of cost or market:
LIFO basis	102,309	109,348
FIFO basis	64,760	13,383
Average cost basis	49,898	56,191
Total inventories	216,967	178,922
Excess of inventories valued at current costs over LIFO	32,000	31,000
Change in income as a result of LIFO basis inventory valuation over FIFO basis valuation	$ 0	$ 100	$ 0