Note 12 - Employee Benefit Plans (Details Textual) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Benefit Plans [Line Items]
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	3.00%
Defined Contribution Plan Safe Harbor Contribution	5.00%
Defined Contribution Plan Employer Matching Contribution Amount	$ 259	$ 206	$ 240
Defined Contribution Plan Employer Safe Harbor Contribution Amount	$ 478	$ 445	$ 441
Employee Stock Purchase Plan 2016 [Member]
Employee Benefit Plans [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Offering Date	10.00%
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in Shares)	30,000
Employee Stock Purchase Plan shares issued	4,052
Employee Stock Purchase Plan expiration date	May 31, 2021
Employee Stock Purchase Plan 2011 [Member]
Employee Benefit Plans [Line Items]
Employee Stock Purchase Plan Shares Issued Since Inception of Plan (in Shares)	17,516