Note 10 - Stockholders' Equity and Stock-based Compensation - Restricted Stock and Restricted Stock Units Activity (Details)	3 Months Ended
	Mar. 31, 2021 shares
Balance (in shares)	481,786
Share-based Payment Arrangement, Option [Member]
Balance (in shares)	533,320
Options Granted (in shares)	0
Options Exercises (in shares)	0
Options Cancelled/forfeited (in shares)	(51,534)
Balance (in shares)	481,786
Restricted Stock and Restricted Stock Units [Member]
Balance (in shares)	732,707
Equity instruments other than options, authorized (in shares)	23,533
Equity instruments other than options, granted (in shares)	0
Equity instruments other than options, vested (in shares)	(24,365)
Equity instruments other than options, cancelled/forfeited (in shares)	(41,944)
Balance (in shares)	689,931
Stock Appreciation Rights (SARs) [Member]
Balance (in shares)	754,582
Options Granted (in shares)	0
Options Exercises (in shares)	(5,000)
Options Cancelled/forfeited (in shares)	(86,991)
Balance (in shares)	662,591