Note 9 - Share Buybacks (Details Textual) - USD ($)							1 Months Ended	2 Months Ended
	Feb. 14, 2020	Dec. 16, 2019	Oct. 24, 2018	Nov. 10, 2017	Apr. 26, 2016	Dec. 22, 2014	Sep. 30, 2016	Dec. 31, 2017	Sep. 30, 2025	Dec. 31, 2024	Mar. 31, 2020	Dec. 31, 2018	Aug. 31, 2018	Dec. 31, 2014
Shares, Outstanding (in shares)									7,016,432	7,016,432
Investment Company, Share Repurchase Plan [Member]
Stock Repurchased and Retired During Period, Shares (in shares)							272,008	128,551
Stock Repurchased During Period, Value							$ 2,000,000	$ 1,100,000
Shares, Outstanding (in shares)								7,302,146
Repurchase Agreement, Date				Nov. 10, 2017	Apr. 26, 2016
Repurchase Agreement, Date of Repurchase			Aug. 31, 2018				Sep. 30, 2016
Investment Company, Share Repurchase Plan [Member] | Maximum [Member]
Stock Repurchase Program, Authorized Amount				$ 2,000,000	$ 2,000,000								$ 2,000,000
Investment Company, Modified Dutch Auction Tender Offer [Member]
Stock Repurchase Program, Authorized Amount		$ 2,000,000				$ 5,044,728
Stock Repurchased During Period, Value			$ 2,000,000
Shares, Outstanding (in shares)											6,893,056	7,178,770
Stock Repurchased During Period, Shares (in shares)	285,714		123,376			859,468
Investment Company, Share Repurchase, Per Share (in dollars per share)	$ 7	$ 0.1	$ 16.21
Stock Repurchase, Purchase Price of Common Stock, Percent						95.00%
Shares Issued, Price Per Share (in dollars per share)														$ 23.2702
Investment Company, Modified Dutch Auction Tender Offer [Member] | Maximum [Member]
Investment Company, Share Repurchase, Per Share (in dollars per share)		8
Investment Company, Modified Dutch Auction Tender Offer [Member] | Minimum [Member]
Investment Company, Share Repurchase, Per Share (in dollars per share)		$ 6
Investment Company, Tender Offer [Member] | Maximum [Member]
Stock Repurchase Program, Authorized Amount						$ 20,000,000