CONDENSED CONSOLIDATED BALANCE SHEETS (Parentheticals) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement Of Financial Position [Abstract]
Accounts receivable, allowance	$ 4,039	$ 4,480
Preferred stock par value	$ 1.00	$ 1.00
Preferred stock shares authorized	1,000,000	1,000,000
Preferred stock shares issued	0	0
Preferred stock shares outstanding	0	0
Common stock par value	$ 0.666	$ 0.666
Common stock shares authorized	70,000,000	70,000,000
Common stock shares issued	49,571,038	49,130,090
Common stock shares outstanding	49,571,038	49,130,090
Treasury stock, shares	1,457,206	1,457,206