Note 8 - Summary of Stock Options (Details Textual) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015	Jul. 22, 2015	Jul. 21, 2015
Two Thousand Five Plan [Member]
Common Stock, Capital Shares Reserved for Future Issuance	2,778
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	2,778
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 102.68
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	1 year 131 days
The 2006 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	39,024
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 11.10
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	6 years 193 days
Conversion of Stock Exchange Ratio	0.0080497
Conversion of Stock, Post Revenue Stock Split Basis, Ratio	0.0010062
The 2013 Plan [Member] | Holdings Greater Than 10 Percent of Shares Outstanding [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	5 years
The 2013 Plan [Member]
Common Stock, Capital Shares Reserved for Future Issuance	130,918
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	1,089,966
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 6.01
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	9 years 131 days
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	4 years
Share-based Compensation Arrangement by Share-based Payment Award, Percentage of Outstanding Stock Maximum	10.00%
Share-based Compensation Arrangement by Share-based Payment Award, Purchase Price of Common Stock, Percent	110.00%
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized				1,262,500	388,949
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	129,267	79,375
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 3.56	$ 2
Employee Stock Option [Member]
Allocated Share-based Compensation Expense	$ 188,000	$ 42,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options	$ 2,598,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	3 years 182 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number	1,131,768		1,022,195
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price	$ 6.42		$ 6.47
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	9 years 135 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross	129,267
Allocated Share-based Compensation Expense	$ 188,000	42,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value	$ 2,000	$ 0