Note 15 - Stock-based Compensation - SARs Activity (Details) - Stock Appreciation Rights (SARs) [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 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)		(4)	(143)
Exercised, aggregate intrinsic value	[1]	$ 115	$ 3,025
Exercised weighted average fair value (in dollars per share)		$ 3.16	$ 3.47
Forfeited, exercise price (in dollars per share)		$ 0	$ 0
Forfeited (in shares)		0
Vested and exercisable (in shares)		490
Vested and exercisable, aggregate intrinsic value	[1]	$ 4,191
Vested and exercisable, weighted average fair value (in dollars per share)		$ 3.60
Vested and exercisable, weighted average remaining contractual life (Year)		4 years 1 month 6 days
Unvested (in shares)		195
Unvested, aggregate intrinsic value	[1]	$ 52
Unvested, weighted average fair value (in dollars per share)		$ 5.80
Unvested, weighted average remaining contractual life (Year)		8 years 6 months
Unvested (in shares)		685	641	731
Outstanding, aggregate intrinsic value	[1]	$ 4,243	$ 10,250	$ 8,422
Unvested, grant date weighted average cost (in dollars per share)		$ 4.23	$ 4.10	$ 3.83
Vested (in shares)		55
Vested, exercise price (in dollars per share)		$ 0
Vested, aggregate intrinsic value	[1]	$ 132
Vested, 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)		24.56
Outstanding, exercise price (in dollars per share)		15.24	14.02	14.02
Vested, 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)		15.24	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, 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)		14.52	15.99
Forfeited, exercise price (in dollars per share)		0	0
Vested and exercisable, exercise price (in dollars per share)		21.69
Unvested, exercise price (in dollars per share)		36.77
Outstanding, exercise price (in dollars per share)		25.99	$ 25.06	$ 22.42
Vested, exercise price (in dollars per share)		$ 30.46

[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.