Note 15 - 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, 2020	Dec. 31, 2019	Dec. 31, 2018
Unvested (in shares)		641	731
Outstanding, aggregate intrinsic value	[1]	$ 10,250	$ 8,422
Unvested, grant date weighted average cost (in dollars per share)		$ 4.10	$ 3.83
Outstanding, weighted average remaining contractual life (Year)		5 years 4 months 24 days	5 years 3 months 18 days	5 years 2 months 12 days
Awarded (in shares)		48	53
Granted, aggregate intrinsic value	[1]	$ 0	$ 213
Shares awarded, grant date weighted average cost (in dollars per share)		$ 5.80	$ 6.24
Exercised (in shares)		(95)	(143)
Exercised, aggregate intrinsic value	[1]	$ 2,361	$ 3,025
Exercised weighted average fair value (in dollars per share)		$ 2.87	$ 3.47
Forfeited, exercise price (in dollars per share)		$ 0	$ 0
Forfeited (in shares)		0
Vested and exercisable (in shares)		402
Vested and exercisable, aggregate intrinsic value	[1]	$ 4,745
Vested and exercisable, weighted average fair value (in dollars per share)		$ 3.78
Vested and exercisable, weighted average remaining contractual life (Year)		4 years 1 month 6 days
Unvested (in shares)		192
Unvested, aggregate intrinsic value	[1]	$ 133
Unvested, weighted average fair value (in dollars per share)		$ 5.81
Unvested, weighted average remaining contractual life (Year)		8 years
Unvested (in shares)		594	641	731
Outstanding, aggregate intrinsic value	[1]	$ 4,878	$ 10,250	$ 8,422
Unvested, grant date weighted average cost (in dollars per share)		$ 4.44	$ 4.10	$ 3.83
Vested in the current year (in shares)		58
Vested in the current year, aggregate intrinsic value	[1]	$ 286
Vested in the current year, weighted average fair value (in dollars per share)		$ 5.02
Minimum [Member]
Outstanding, exercise price (in dollars per share)		14.02	14.02
Granted, exercise price (in dollars per share)		37.30	36.65
Exercised, exercise price (in dollars per share)		14.02	14.02
Vested and exercisable, exercise price (in dollars per share)		15.24
Unvested, exercise price (in dollars per share)		25.76
Outstanding, exercise price (in dollars per share)		15.24	14.02	14.02
Vested in the current year, exercise price (in dollars per share)		22.96
Maximum [Member]
Outstanding, exercise price (in dollars per share)		40.00	40.00
Granted, exercise price (in dollars per share)		37.30	38.18
Exercised, exercise price (in dollars per share)		25.76	22.96
Vested and exercisable, exercise price (in dollars per share)		40.00
Unvested, exercise price (in dollars per share)		40.00
Outstanding, exercise price (in dollars per share)		40.00	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)		25.06	22.42
Granted, exercise price (in dollars per share)		37.30	37.01
Exercised, exercise price (in dollars per share)		16.32	15.99
Forfeited, exercise price (in dollars per share)		0	0
Vested and exercisable, exercise price (in dollars per share)		23.00
Unvested, exercise price (in dollars per share)		36.77
Outstanding, exercise price (in dollars per share)		27.45	$ 25.06	$ 22.42
Vested in the current year, exercise price (in dollars per share)		$ 30.79

[1] 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.