Condensed Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Accumulated Depreciation	$ 240,509	$ 226,366
Preferred stock, par value (in usd per share)	$ 1	$ 1
Preferred stock, shares authorized	200,000	200,000
Preferred stock, shares issued	0	0
Common stock, par value (in usd per share)	$ 1	$ 1
Common stock, shares authorized	50,000,000	50,000,000
Common stock, shares issued	29,051,030	28,162,497
Common Stock held in treasury, at cost (in shares)	1,152,340	1,054,364