Note 9 - Stockholders' Equity - Options Classified Into Range of Exercise Price (Details) - $ / shares		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019
Outstanding, number of options and SARs (in shares)	[2]	289,069	[1]	642,253
Outstanding, Weighted average remaining contractual term (Year)		3 years 7 months 6 days	[1]	3 years 6 months
Outstanding, weighted average exercise price (in dollars per share)		$ 22.42
Exercisable, Number of shares (in shares)	[2],[3]	289,069
Exercisable, weighted average remaining contractual life (Year)		3 years 7 months 6 days
Exercisable, Weighted average exercise price (in dollars per share)	[3]	$ 22.42
Exercise Price Range 1 [Member]
Range of exercise price, lower limit (in dollars per share)		18.62
Range of exercise price, upper limit (in dollars per share)
Outstanding, number of options and SARs (in shares)		78,320
Outstanding, Weighted average remaining contractual term (Year)		2 years 1 month 6 days
Outstanding, weighted average exercise price (in dollars per share)		$ 15.57
Exercisable, Number of shares (in shares)		78,320
Exercisable, weighted average remaining contractual life (Year)		2 years 1 month 6 days
Exercisable, Weighted average exercise price (in dollars per share)		$ 15.57
Exercise Price Range 2 [Member]
Range of exercise price, lower limit (in dollars per share)		19.83
Range of exercise price, upper limit (in dollars per share)
Outstanding, number of options and SARs (in shares)		86,949
Outstanding, Weighted average remaining contractual term (Year)		3 years 8 months 12 days
Outstanding, weighted average exercise price (in dollars per share)		$ 19.42
Exercisable, Number of shares (in shares)		86,949
Exercisable, weighted average remaining contractual life (Year)		3 years 8 months 12 days
Exercisable, Weighted average exercise price (in dollars per share)		$ 19.42
Exercise Price Range 3 [Member]
Range of exercise price, lower limit (in dollars per share)		30.60
Range of exercise price, upper limit (in dollars per share)
Outstanding, number of options and SARs (in shares)		123,800
Outstanding, Weighted average remaining contractual term (Year)		4 years 6 months
Outstanding, weighted average exercise price (in dollars per share)		$ 28.85
Exercisable, Number of shares (in shares)		123,800
Exercisable, weighted average remaining contractual life (Year)		4 years 6 months
Exercisable, Weighted average exercise price (in dollars per share)		$ 28.85

[1] Due to the ceiling imposed on the SAR grants, the outstanding amount equals a maximum of 280,427 shares of the Company's common stock issuable upon exercise.

[2] 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.

[3] Due to the ceiling imposed on the SAR grants, the exercisable amount equals a maximum of 280,427 shares of the Company's common stock issuable upon exercise.