Note 1 - Organization and Summary of Significant Accounting Policies (Tables)
|12 Months Ended|
Dec. 31, 2017
|Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]||
Tabular disclosure of the significant assumptions used during the year to estimate the fair value of stock options, including, but not limited to: (a) expected term of share options and similar instruments, (b) expected volatility of the entity's shares, (c) expected dividends, (d) risk-free rate(s), and (e) discount for post-vesting restrictions.
Reference 1: http://www.xbrl.org/2003/role/presentationRef