Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 1,176	$ 974
Property, plant and equipment, accumulated depreciation	146,735	145,137
Other intangible assets, accumulated amortization	1,061	650
Other assets, deferred income taxes	4,691	3,000
Other long-term liabilities, deferred income taxes	$ 22,254	$ 20,672
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)	120,398,225	120,146,720
Treasury stock, shares (in shares)	58,907,485	58,879,742