Note 6 - Fair Value Measurements - Assets Measured at Fair Value on Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands		Dec. 31, 2023	Dec. 31, 2022
Assets, Fair Value Disclosure		$ 40,251	$ 34,307
Cash and Cash Equivalents [Member]
Assets, Fair Value Disclosure	[1]	40,229	17,722
Equity Securities [Member]
Assets, Fair Value Disclosure		22	69
Mutual Fund [Member]
Assets, Fair Value Disclosure		0	16,516
Marketable Securities [Member]
Assets, Fair Value Disclosure		22	16,585
Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure		40,251	17,791
Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member]
Assets, Fair Value Disclosure	[1]	40,229	17,722
Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member]
Assets, Fair Value Disclosure		22	69
Fair Value, Inputs, Level 1 [Member] | Mutual Fund [Member]
Assets, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 1 [Member] | Marketable Securities [Member]
Assets, Fair Value Disclosure		22	69
Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure		0	16,516
Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member]
Assets, Fair Value Disclosure	[1]	0	0
Fair Value, Inputs, Level 2 [Member] | Equity Securities [Member]
Assets, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 2 [Member] | Mutual Fund [Member]
Assets, Fair Value Disclosure		0	16,516
Fair Value, Inputs, Level 2 [Member] | Marketable Securities [Member]
Assets, Fair Value Disclosure		0	16,516
Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 3 [Member] | Cash and Cash Equivalents [Member]
Assets, Fair Value Disclosure	[1]	0	0
Fair Value, Inputs, Level 3 [Member] | Equity Securities [Member]
Assets, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 3 [Member] | Mutual Fund [Member]
Assets, Fair Value Disclosure		0	0
Fair Value, Inputs, Level 3 [Member] | Marketable Securities [Member]
Assets, Fair Value Disclosure		$ 0	$ 0

[1] As of December 31, 2023 and 2022, included investments in money market mutual funds managed by GAMCO Investors, Inc.