Note 3 - Summary of Significant Accounting Policies (Details Textual)	3 Months Ended
	Mar. 31, 2022 USD ($) shares	Mar. 31, 2021 shares	Dec. 31, 2021 USD ($)
Number of Operating Segments	2
Short-Term Investments, Total	$ 12,400,000		$ 13,900,000
Accounts Receivable, Allowance for Credit Loss, Ending Balance	10,000		10,000
Unrecognized Tax Benefits, Ending Balance	0		$ 0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense, Total	$ 0
Open Tax Year	2018 2019 2020
Weighted Average Number of Shares Outstanding, Basic, Total (in shares) | shares	69,013,001	66,578,435
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount (in shares) | shares	7,543,252	6,092,193