Note 5 - Fair Value Measurements - Assets Measured at Fair Value on Recurring Basis (Details) - Fair Value, Recurring [Member] - USD ($) $ in Thousands		Sep. 30, 2025	Dec. 31, 2024
Assets, Fair Value Disclosure		$ 40,965	$ 41,202
Cash and Cash Equivalents [Member]
Assets, Fair Value Disclosure	[1]	40,935	41,185
Equity Securities [Member]
Assets, Fair Value Disclosure		30	17
Marketable Securities [Member]
Assets, Fair Value Disclosure		30	17
Fair Value, Inputs, Level 1 [Member]
Assets, Fair Value Disclosure		40,965	41,202
Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member]
Assets, Fair Value Disclosure	[1]	40,935	41,185
Fair Value, Inputs, Level 1 [Member] | Equity Securities [Member]
Assets, Fair Value Disclosure		30	17
Fair Value, Inputs, Level 1 [Member] | Marketable Securities [Member]
Assets, Fair Value Disclosure		30	17
Fair Value, Inputs, Level 2 [Member]
Assets, Fair Value Disclosure	[1]	0	0
Fair Value, Inputs, Level 3 [Member]
Assets, Fair Value Disclosure	[1]	$ 0	$ 0

[1] As of September 30, 2025 and December 31, 2024, included investments in money market mutual funds managed or advised by GAMCO Investors, Inc.