CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL POSITION (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 1,319	$ 1,682
Property, plant and equipment, accumulated depreciation	$ 363,927	$ 365,844
Capital Stock, par value (in dollars per share)	$ 1	$ 1
Capital Stock, authorized shares (shares)	50,000,000	50,000,000
Capital Stock, shares issued (shares)	18,722,000	18,677,000
Capital Stock, shares outstanding (shares)	18,722,000	18,677,000