Note 7 - Related Party Transactions - Transactions With Related Parties (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2024	Dec. 31, 2023
Income	$ 1,157	$ 1,179	$ 1,068	$ 888	$ 995	$ 978	$ 721	$ 984	$ 4,292	$ 3,678
Expense	(912)	$ (1,041)	$ (831)	$ (809)	(666)	$ (779)	$ (853)	$ (734)	(3,593)	(3,032)
Total assets	43,145				41,850				43,145	41,850
Liabilities	1,905				1,168				1,905	1,168
GAMCO Investors, Inc. [Member]
Income									1,712	1,677
Expense									0	0
Total assets	34,242				32,568				34,242	32,568
Liabilities	0				0				0	0
Mtron Industries Inc [Member]
Income									0	0
Expense									(57)	20
Total assets	0				0				0	0
Liabilities	59				0				59	0
Related Party [Member]
Income									1,712	1,677
Expense									(57)	20
Total assets	34,242				32,568				34,242	32,568
Liabilities	$ 59				$ 0				$ 59	$ 0