CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Trade receivables, allowance for doubtful receivables	$ 3,266	$ 3,404
Indefinite-lived and amortizable intangible assets, accumulated amortization	$ 88,120	$ 66,550
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, Authorized (in shares)	800,000,000	800,000,000
Common stock, Issued (in shares)	324,418,632	324,418,632
Treasury stock (in shares)	109,487,979	109,930,832