Note 7 - Share-based Compensation - Stock Option Transactions (Details) - USD ($) $ / shares in Units, $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2021	Dec. 31, 2020	Jan. 01, 2021
Outstanding, options (in shares)		970,022
Outstanding, weighted average exercise price (in dollars per share)		$ 12.92
Outstanding, weighted average remaining life (Year)		3 years 5 months 4 days	3 years 8 months 26 days
Outstanding, aggregate intrinsic value		$ 6,487		$ 11,128
Granted (in shares)	[1]	143,543
Granted, weighted average exercise price (in dollars per share)	[1]	$ 25.02
Exercised (in shares)		(262,960)
Exercised, weighted average exercise price (in dollars per share)		$ 10.10
Lapsed or cancelled (in shares)		(19,126)
Lapsed or cancelled, weighted average exercise price (in dollars per share)		$ 14.90
Outstanding, options (in shares)		831,479	970,022
Outstanding, weighted average exercise price (in dollars per share)		$ 15.86	$ 12.92
Exercisable, options (in shares)		487,161
Exercisable, weighted average exercise price, options (in dollars per share)		$ 14.66
Exercisable, weighted average remaining life, options (Year)		2 years 9 months 29 days
Exercisable, aggregate intrinsic value, options		$ 4,231

[1] The weighted average grant date fair value of stock options granted was $10.28 per share.