Accounts Receivable and Inventories (Details) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Accounts receivable
Trade accounts receivable	$ 279,800,000		$ 248,354,000
Less: Allowance for doubtful accounts	(11,801,000)		(11,800,000)
Trade accounts receivable, net	267,999,000		236,554,000
Other receivables	21,192,000		21,053,000
Provision for doubtful accounts related to trade accounts receivable	(22,000)	$ (146,000)
Inventories
Finished goods	23,175,000		26,464,000
Work-in-process	18,172,000		22,815,000
Contracts-in-process	65,693,000		54,044,000
Raw materials and purchased parts	58,987,000		61,450,000
Stores and supplies	24,404,000		22,908,000
Inventories	190,431,000		187,681,000
Inventory for Contracts
Contract costs accumulated to date	98,240,000		90,276,000
Estimated loss provisions for contracts-in-process	(32,547,000)		(36,232,000)
Contracts-in-process	65,693,000		54,044,000
Loss provision that exceeds accumulated contract costs	6,800,000		6,700,000
Customer Advances and Deposits	102,500,000		101,100,000
Loss on Contracts	0		$ 45,100,000
Contracts Revenue	$ 0	$ 0