Note 17 - Stock-based Compensation - SARs Activity (Details) - Stock Appreciation Rights (SARs) [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2021	Dec. 31, 2020	Dec. 31, 2019
Unvested (in shares)		593	641
Outstanding, aggregate intrinsic value	[1]	$ 7,706	$ 10,250
Unvested, grant date weighted average cost (in dollars per share)		$ 4.44	$ 4.10
Outstanding, weighted average remaining contractual life (Year)		5 years 2 months 12 days	5 years 1 month 6 days	5 years 3 months 18 days
Awarded (in shares)		31	48
Granted, aggregate intrinsic value	[1]	$ 251	$ 154
Shares awarded, grant date weighted average cost (in dollars per share)		$ 9.69	$ 5.80
Exercised (in shares)		(77)	(96)
Exercised, aggregate intrinsic value	[1]	$ 2,815	$ 2,401
Exercised weighted average fair value (in dollars per share)		$ 2.58	$ 2.88
Forfeited (in shares)		0
Vested and exercisable (in shares)		388
Vested and exercisable, aggregate intrinsic value	[1]	$ 12,492
Vested and exercisable, weighted average fair value (in dollars per share)		$ 4.30
Vested and exercisable, weighted average remaining contractual life (Year)		4 years 1 month 6 days
Unvested (in shares)		159
Unvested, aggregate intrinsic value	[1]	$ 2,926
Unvested, weighted average fair value (in dollars per share)		$ 6.70
Unvested, weighted average remaining contractual life (Year)		7 years 9 months 18 days
Unvested (in shares)		547	593	641
Outstanding, aggregate intrinsic value	[1]	$ 15,417	$ 7,706	$ 10,250
Unvested, grant date weighted average cost (in dollars per share)		$ 5.00	$ 4.44	$ 4.10
Vested in the current year (in shares)		53
Vested in the current year, aggregate intrinsic value	[1]	$ 1,316
Vested in the current year (in dollars per share)		$ 5.40
Minimum [Member]
Outstanding, exercise price (in dollars per share)		15.24	14.02
Granted, exercise price (in dollars per share)		47.17	37.30
Exercised, exercise price (in dollars per share)		15.24	14.02
Vested and exercisable, exercise price (in dollars per share)		15.24
Unvested, exercise price (in dollars per share)		33.08
Outstanding, exercise price (in dollars per share)		15.24	15.24	14.02
Vested in the current year, exercise price (in dollars per share)		25.76
Maximum [Member]
Outstanding, exercise price (in dollars per share)		40.00	40.00
Granted, exercise price (in dollars per share)		50.71	37.30
Exercised, exercise price (in dollars per share)		15.84	25.76
Vested and exercisable, exercise price (in dollars per share)		40.00
Unvested, exercise price (in dollars per share)		50.71
Outstanding, exercise price (in dollars per share)		50.71	40.00	40.00
Vested in the current year, exercise price (in dollars per share)		40.00
Weighted Average [Member]
Outstanding, exercise price (in dollars per share)		27.47	25.06
Granted, exercise price (in dollars per share)		50.48	37.30
Exercised, exercise price (in dollars per share)		15.31	16.33
Forfeited, exercise price (in dollars per share)		0	0
Vested and exercisable, exercise price (in dollars per share)		26.49
Unvested, exercise price (in dollars per share)		40.20
Outstanding, exercise price (in dollars per share)		30.46	$ 27.47	$ 25.06
Vested in the current year, exercise price (in dollars per share)		$ 34.00

[1] Aggregate intrinsic value for SARs is defined as the amount by which the current market price of the underlying stock exceeds the exercise or grant price.