Condensed Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Receivables allowance for doubtful accounts (in dollars)	$ 24	$ 24
Preferred stock, percentage non-cumulative	5.00%	5.00%
Preferred stock, par value (in dollars per share)	$ 10	$ 10
Preferred stock, shares authorized (shares)	1,000	1,000
Preferred stock, shares issued (shares)	437	437
Preferred stock, shares outstanding (shares)	437	437
Common stock, shares authorized (shares)	40,000,000	40,000,000
Common stock, shares issued (shares)	18,115,965	16,844,596
Common stock, shares outstanding (shares)	16,797,420	16,797,420
Treasury stock (shares)	1,271,369	1,318,545