Note 4 - Fair Value (Tables)
|3 Months Ended|
Mar. 31, 2019
|Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]||
Tabular disclosure of assets and liabilities, including [financial] instruments measured at fair value that are classified in stockholders' equity, if any, that are measured at fair value on a recurring basis. The disclosures contemplated herein include the fair value measurements at the reporting date by the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3).
Reference 1: http://www.xbrl.org/2003/role/disclosureRef