Note 8 - Stock-based Compensation - Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Balance, number of shares (in shares)	70,000	60,000
Balance, weighted average exercise price per share (in dollars per share)	$ 7.71	$ 8
Balance, weighted average fair value at grant date (in dollars per share)	$ 0		$ 0	$ 0
Balance, weighted average remaining contractual life (Year)	3 years 40 days	3 years 313 days	4 years 273 days
Balance, intrinsic value		$ 0	$ 0
Options granted, number of shares (in shares)		10,000	60,000
Options granted, weighted average exercise price per share (in dollars per share)		$ 6	$ 8
Options granted, intrinsic value			$ 0
Options exercised, number of shares (in shares)		0	0
Options exercised, weighted average exercise price per share (in dollars per share)		$ 0	$ 0
Options exercised, intrinsic value		$ 0	$ 0
Options expired, number of shares (in shares)		0
Options expired, weighted average exercise price per share (in dollars per share)		$ 0
Options expired, weighted average fair value at grant date (in dollars per share)			$ 0
Options expired, intrinsic value		$ 0	$ 0
Options granted, weighted average remaining contractual life (Year)
Balance, number of shares (in shares)	70,000	70,000	60,000
Balance, weighted average exercise price per share (in dollars per share)	$ 7.71	$ 7.71	$ 8
Balance, intrinsic value			$ 0	$ 0