Note 3 - Revenue From Contracts With Customers - Changes in Contract Liabilities (Details) - USD ($) |
3 Months Ended | |
|---|---|---|
Mar. 31, 2021 |
Mar. 31, 2020 |
|
| Total deferred revenue, beginning of period | $ 700,000 | $ 700,000 |
| Revenue recognized from satisfaction of performance obligations | ||
| Total deferred revenue, end of period | $ 700,000 | $ 700,000 |
| X | ||||||||||
- Definition Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|
| X | ||||||||||
- Definition Amount of revenue recognized that was previously included in balance of obligation to transfer good or service to customer for which consideration from customer has been received or is due. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
|