Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts and notes receivable, allowances	$ 17,925	$ 16,280
Property and equipment, accumulated depreciation	$ 248,482	$ 239,581
Common stock, par value (in USD per share)	$ 2	$ 2
Common stock, authorized (shares)	200,000,000	200,000,000
Common stock, issued (shares)	61,812,000	61,476,000
Common stock, outstanding (shares)	61,812,000	61,476,000