Note 7 - Stock-based Compensation (Details Textual) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
	Jan. 02, 2015	Sep. 30, 2015	Jun. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
The 2014 Employee Stock Purchase Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award Number of Annual Additional Shares Percentage	1.00%
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	281,000
The 2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized		304,991			304,991		140,500
Stock Issued During Period, Shares, Employee Stock Purchase Plans			5,864		5,864
Common Stock, Capital Shares Reserved for Future Issuance		299,127			299,127
Allocated Share-based Compensation Expense		$ 5,000			$ 27,000
Common Stock, Capital Shares Reserved for Future Issuance		2,739,254			2,739,254		1,947,849
Allocated Share-based Compensation Expense		$ 611		$ 185	$ 1,494	$ 234