Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accounts and notes receivable, allowances	$ 21,456	$ 19,618
Property and equipment, accumulated depreciation	$ 297,297	$ 270,105
Common stock, par value (in USD per share)	$ 2	$ 2
Common stock, authorized (shares)	200,000,000	200,000,000
Common stock, issued (shares)	62,964,000	62,294,000
Common stock, outstanding (shares)	62,964,000	62,294,000