Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Allowances for accounts receivable	$ 8,031	$ 7,533
Accumulated amortization of intangibles	$ 65,766	$ 62,274
Preferred stock, par value	$ 1	$ 1
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Common stock, par value	$ 1	$ 1
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	87,850,292	87,850,292
Treasury stock, shares	32,477,615	32,017,754