Note 10 - Common Stock and Stock-based Compensation Plans - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended			6 Months Ended		12 Months Ended
		Jun. 30, 2022		Jun. 30, 2021	Jun. 30, 2022		Dec. 31, 2021
Outstanding, Number of shares (in shares)	[1]				126,000
Outstanding, Weighted average exercise price (in dollars per share)					$ 20.06
Outstanding, Weighted average remaining contractual term (Year)					2 years 6 months	[2]	2 years 7 months 6 days
Outstanding, Aggregated intrinsic value		$ 1,438	[2]		$ 1,438	[2]	$ 2,921
Granted, Number of shares (in shares)		0		0	0	[1]
Exercised, Number of shares (in shares)	[1]				(17,000)
Exercised, Weighted average exercise price (in dollars per share)					$ 18.08
Forfeited or expired, Number of shares (in shares)	[1]				0
Outstanding, Number of shares (in shares)	[1]	109,000	[2]		109,000	[2]	126,000
Outstanding, Weighted average exercise price (in dollars per share)		$ 20.37	[2]		$ 20.37	[2]	$ 20.06
Exercisable, Number of shares (in shares)	[1],[3]	109,000			109,000
Exercisable, Weighted average exercise price (in dollars per share)	[3]	$ 20.37			$ 20.37
Exercisable, Weighted average remaining contractual term (Year)	[3]				2 years 6 months
Exercisable, Aggregated intrinsic value	[3]	$ 1,438			$ 1,438

[1] The SAR units are convertible for a maximum number of shares of the Company’s common stock equal to 75% of the SAR units subject to the grant.

[2] Due to the ceiling imposed on the SAR grants, the outstanding amount equals a maximum of 108,250 shares of the Company’s common stock issuable upon exercise.

[3] Due to the ceiling imposed on the SAR grants, the exercisable amount equals a maximum of 108,250 shares of the Company’s common stock issuable upon exercise.