Note 9 - Share-based Compensation - Stock Option Activity (Details)	6 Months Ended
	Jun. 30, 2019 $ / shares shares
Options outstanding at beginning of year (in shares) | shares	624,256
Options outstanding at beginning of year (in dollars per share) | $ / shares	$ 8.87
Number of shares, granted (in shares) | shares
Weighted average exercise price, granted (in dollars per share) | $ / shares
Number of shares, exercised (in shares) | shares
Weighted average exercise price, exercised (in dollars per share) | $ / shares
Number of shares, forfeited prior to vesting (in shares) | shares
Weighted average exercise price, forfeited prior to vesting (in dollars per share) | $ / shares
Number of shares, canceled or expired (in shares) | shares	(54,671)
Weighted average exercise price, canceled or expired (in dollars per share) | $ / shares	$ 9.44
Options outstanding at June 30, 2019 (in shares) | shares	569,585
Options outstanding at June 30, 2019 (in dollars per share) | $ / shares	$ 8.81
Options exercisable at end of June 30, 2019 (in shares) | shares	527,352
Options exercisable at end of June 30, 2019 (in dollars per share) | $ / shares	$ 8.63