Note 4 - Fair Value Measurements - Fair Value of Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Liabilities:
Convertible preferred stock warrant liability		$ 275
Maturity date preferred stock warrant liability		10
Convertible shareholder notes derivative liability		1,044
Fair Value, Measurements, Recurring [Member]
Assets:
Cash and cash equivalents	21,352	3,557
Liabilities:
Convertible preferred stock warrant liability		275
Maturity date preferred stock warrant liability		10
Convertible shareholder notes derivative liability		1,044
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Cash and cash equivalents	21,352	3,557
Liabilities:
Convertible preferred stock warrant liability
Maturity date preferred stock warrant liability
Convertible shareholder notes derivative liability
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Cash and cash equivalents
Liabilities:
Convertible preferred stock warrant liability
Maturity date preferred stock warrant liability
Convertible shareholder notes derivative liability
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Assets:
Cash and cash equivalents
Liabilities:
Convertible preferred stock warrant liability		275
Maturity date preferred stock warrant liability		10
Convertible shareholder notes derivative liability		$ 1,044