Note 3 - Revenue Recognition (Tables)
|3 Months Ended|
Mar. 31, 2019
|Disaggregation of Revenue [Table Text Block]||
Tabular disclosure of disaggregation of revenue into categories depicting how nature, amount, timing, and uncertainty of revenue and cash flows are affected by economic factor.
Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef