Condensed Consolidated Balance Sheets (Current Period Unaudited) (Parentheticals) - $ / shares	Jun. 30, 2018	Dec. 31, 2017
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, authorized (in shares)	50,000,000	50,000,000
Common stock, issued (in shares)	21,381,779	21,381,779
Treasury stock (in shares)	4,802,475	4,383,553
Undesignated Par Value [Member]
Preferred stock, no par value (in dollars per share)	$ 0	$ 0	[1]
Preferred stock, authorized (in shares)	1,000,000	1,000,000	[1]
Designated Par Value [Member]
Preferred stock, authorized (in shares)	25,000	25,000	[1]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01	[1]
Preferred stock, outstanding (in shares)	0	0	[1]

[1] Derived from audited financial statements