CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL POSITION (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 738	$ 695
Property, plant and equipment, accumulated depreciation	$ 258,051	$ 237,150
Capital Stock, par value (in dollars per share)	$ 1	$ 1
Capital Stock, authorized shares (shares)	50,000,000	50,000,000
Capital Stock, shares outstanding (shares)	17,973,000	17,957,000