Note 15 - Stock-based Compensation - Summary of Information About Stock-based Awards Outstanding (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Number of shares outstanding (in shares)	2,240	1,792
Weighted average remaining contractual life in years, options outstanding (Year)	3 years 10 months 24 days	3 years 9 months 18 days
Aggregate intrinsic value, options outstanding	$ 73,039	$ 43,277
Number of shares exercisable (in shares)	704	479
Aggregate intrinsic value, options exercisable	$ 27,211	$ 11,729
Weighted average remaining contractual life in years, options exercisable (Year)	2 years 7 months 6 days	3 years 2 months 12 days
Exercise Price 1 [Member]
Number of shares outstanding (in shares)	85	59
Weighted average remaining contractual life in years, options outstanding (Year)	2 years 1 month 6 days	1 year 6 months
Aggregate intrinsic value, options outstanding	$ 7,677	$ 4,369
Number of shares exercisable (in shares)	0	0
Aggregate intrinsic value, options exercisable	$ 0	$ 0
Exercise Price 2 [Member]
Number of shares outstanding (in shares)	235	427
Weighted average remaining contractual life in years, options outstanding (Year)	1 year 6 months	2 years 6 months
Aggregate intrinsic value, options outstanding	$ 11,129	$ 13,517
Number of shares exercisable (in shares)	235	230
Aggregate intrinsic value, options exercisable	$ 11,129	$ 7,295
Exercise price (in dollars per share)	$ 42.87	$ 42.87
Weighted average remaining contractual life in years, options exercisable (Year)	1 year 6 months	2 years 6 months
Exercise Price 3 [Member]
Number of shares outstanding (in shares)	15	15
Weighted average remaining contractual life in years, options outstanding (Year)	2 years 10 months 24 days	3 years 10 months 24 days
Aggregate intrinsic value, options outstanding	$ 642	$ 406
Number of shares exercisable (in shares)	15	15
Aggregate intrinsic value, options exercisable	$ 642	$ 406
Exercise price (in dollars per share)	$ 47.46	$ 47.46
Weighted average remaining contractual life in years, options exercisable (Year)	2 years 10 months 24 days	3 years 10 months 24 days
Exercise Price 4 [Member]
Number of shares outstanding (in shares)	8	8
Weighted average remaining contractual life in years, options outstanding (Year)	4 years	5 years
Aggregate intrinsic value, options outstanding	$ 309	$ 182
Number of shares exercisable (in shares)	0	0
Aggregate intrinsic value, options exercisable	$ 0	$ 0
Exercise price (in dollars per share)	$ 51.71	$ 51.71
Weighted average remaining contractual life in years, options exercisable (Year)	4 years	0 years
Exercise Price 5 [Member]
Number of shares outstanding (in shares)	31	35
Weighted average remaining contractual life in years, options outstanding (Year)	3 years 10 months 24 days	4 years 10 months 24 days
Aggregate intrinsic value, options outstanding	$ 1,164	$ 756
Number of shares exercisable (in shares)	21	15
Aggregate intrinsic value, options exercisable	$ 792	$ 329
Exercise price (in dollars per share)	$ 53.16	$ 53.16
Weighted average remaining contractual life in years, options exercisable (Year)	3 years 10 months 24 days	4 years 10 months 24 days
Exercise Price 6 [Member]
Number of shares outstanding (in shares)	486	783
Weighted average remaining contractual life in years, options outstanding (Year)	3 years 6 months	4 years 6 months
Aggregate intrinsic value, options outstanding	$ 17,893	$ 16,498
Number of shares exercisable (in shares)	129	0
Aggregate intrinsic value, options exercisable	$ 4,719	$ 0
Exercise price (in dollars per share)	$ 53.44	$ 53.44
Weighted average remaining contractual life in years, options exercisable (Year)	3 years 6 months	0 years
Exercise Price 7 [Member]
Number of shares outstanding (in shares)	296	296
Weighted average remaining contractual life in years, options outstanding (Year)	2 years 10 months 24 days	3 years 10 months 24 days
Aggregate intrinsic value, options outstanding	$ 10,384	$ 5,724
Number of shares exercisable (in shares)	213	131
Aggregate intrinsic value, options exercisable	$ 7,484	$ 2,527
Exercise price (in dollars per share)	$ 55.16	$ 55.16
Weighted average remaining contractual life in years, options exercisable (Year)	2 years 10 months 24 days	3 years 10 months 24 days
Exercise Price 8 [Member]
Number of shares outstanding (in shares)	15	30
Weighted average remaining contractual life in years, options outstanding (Year)	3 years 7 months 6 days	4 years 7 months 6 days
Aggregate intrinsic value, options outstanding	$ 485	$ 497
Number of shares exercisable (in shares)	15	30
Aggregate intrinsic value, options exercisable	$ 485	$ 497
Exercise price (in dollars per share)	$ 57.97	$ 57.97
Weighted average remaining contractual life in years, options exercisable (Year)	3 years 7 months 6 days	4 years 7 months 6 days
Exercise Price 9 [Member]
Number of shares outstanding (in shares)	1	12
Weighted average remaining contractual life in years, options outstanding (Year)	1 year 6 months	2 years 6 months
Aggregate intrinsic value, options outstanding	$ 33	$ 187
Number of shares exercisable (in shares)	0	6
Aggregate intrinsic value, options exercisable	$ 0	$ 94
Exercise price (in dollars per share)	$ 58.79	$ 58.79
Weighted average remaining contractual life in years, options exercisable (Year)	1 year 6 months	2 years 6 months
Exercise Price 10 [Member]
Number of shares outstanding (in shares)	94	98
Weighted average remaining contractual life in years, options outstanding (Year)	2 years 10 months 24 days	3 years 10 months 24 days
Aggregate intrinsic value, options outstanding	$ 2,525	$ 1,094
Number of shares exercisable (in shares)	68	52
Aggregate intrinsic value, options exercisable	$ 1,843	$ 581
Exercise price (in dollars per share)	$ 63.35	$ 63.35
Weighted average remaining contractual life in years, options exercisable (Year)	2 years 10 months 24 days	3 years 10 months 24 days
Exercise Price 11 [Member]
Number of shares outstanding (in shares)	45	4
Weighted average remaining contractual life in years, options outstanding (Year)	5 years 6 months	5 years 7 months 6 days
Aggregate intrinsic value, options outstanding	$ 1,219	$ 11
Number of shares exercisable (in shares)	0	0
Aggregate intrinsic value, options exercisable	$ 0	$ 0
Exercise price (in dollars per share)	$ 63.40	$ 71.71
Weighted average remaining contractual life in years, options exercisable (Year)	5 years 6 months
Exercise Price 12 [Member]
Number of shares outstanding (in shares)	12	15
Weighted average remaining contractual life in years, options outstanding (Year)	5 years 10 months 24 days	5 years 8 months 12 days
Aggregate intrinsic value, options outstanding	$ 269	$ 36
Number of shares exercisable (in shares)	0	0
Aggregate intrinsic value, options exercisable	$ 0	$ 0
Exercise price (in dollars per share)	$ 67.54	$ 72.14
Weighted average remaining contractual life in years, options exercisable (Year)	5 years 10 months 24 days
Exercise Price 13 [Member]
Number of shares outstanding (in shares)	47	10
Weighted average remaining contractual life in years, options outstanding (Year)	5 years 4 months 24 days	5 years 10 months 24 days
Aggregate intrinsic value, options outstanding	$ 1,027	$ 0
Number of shares exercisable (in shares)	0	0
Aggregate intrinsic value, options exercisable	$ 0	$ 0
Exercise price (in dollars per share)	$ 68.34	$ 76.43
Weighted average remaining contractual life in years, options exercisable (Year)	5 years 4 months 24 days
Exercise Price 14 [Member]
Number of shares outstanding (in shares)	842
Weighted average remaining contractual life in years, options outstanding (Year)	5 years 4 months 24 days
Aggregate intrinsic value, options outstanding	$ 17,820
Number of shares exercisable (in shares)	0
Aggregate intrinsic value, options exercisable	$ 0
Exercise price (in dollars per share)	$ 69.14
Weighted average remaining contractual life in years, options exercisable (Year)	5 years 4 months 24 days
Exercise Price 15 [Member]
Number of shares outstanding (in shares)	4
Weighted average remaining contractual life in years, options outstanding (Year)	4 years 7 months 6 days
Aggregate intrinsic value, options outstanding	$ 74
Number of shares exercisable (in shares)	0
Aggregate intrinsic value, options exercisable	$ 0
Exercise price (in dollars per share)	$ 71.71
Weighted average remaining contractual life in years, options exercisable (Year)	4 years 7 months 6 days
Exercise Price 16 [Member]
Number of shares outstanding (in shares)	15
Weighted average remaining contractual life in years, options outstanding (Year)	4 years 8 months 12 days
Aggregate intrinsic value, options outstanding	$ 272
Number of shares exercisable (in shares)	0
Aggregate intrinsic value, options exercisable	$ 0
Exercise price (in dollars per share)	$ 72.14
Weighted average remaining contractual life in years, options exercisable (Year)	4 years 8 months 12 days
Exercise Price 17 [Member]
Number of shares outstanding (in shares)	8
Weighted average remaining contractual life in years, options outstanding (Year)	4 years 10 months 24 days
Aggregate intrinsic value, options outstanding	$ 117
Number of shares exercisable (in shares)	8
Aggregate intrinsic value, options exercisable	$ 117
Exercise price (in dollars per share)	$ 76.43
Weighted average remaining contractual life in years, options exercisable (Year)	4 years 10 months 24 days
Exercise Price 18 [Member]
Number of shares outstanding (in shares)	1
Weighted average remaining contractual life in years, options outstanding (Year)	2 years 9 months 18 days
Aggregate intrinsic value, options outstanding	$ 0
Number of shares exercisable (in shares)	0
Aggregate intrinsic value, options exercisable	$ 0
Exercise price (in dollars per share)	$ 90.28
Weighted average remaining contractual life in years, options exercisable (Year)	2 years 9 months 18 days