Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 905	$ 1,028
Property, plant and equipment, accumulated depreciation	137,002	141,388
Other intangible assets, accumulated amortization	$ 1,846	$ 1,471
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	250,000,000	250,000,000
Common stock, shares issued (in shares)	120,739,949	120,436,735
Treasury stock, shares (in shares)	58,764,171	58,791,630