Note 4 - Fair Value Measurements - Discounted Cash Flow Assumptions (Details)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Minimum [Member]
Time-to-liquidity (Year)	2 years	2 years
Discount rate	4.00%	4.90%
Maximum [Member]
Time-to-liquidity (Year)	3 years	3 years
Discount rate	8.30%	10.10%