Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 1,251	$ 1,249
Property, plant and equipment, accumulated depreciation	175,238	171,415
Other intangible assets, accumulated amortization	855	650
Other assets, deferred income taxes	4,756	3,000
Other long-term liabilities, deferred income taxes	$ 22,733	$ 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)	120,264,526	120,146,720
Treasury stock, shares (in shares)	58,892,253	58,879,742