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, 2019	Dec. 31, 2018
Number of shares outstanding (in shares)	1,792	2,527
Weighted average remaining contractual life in years, options outstanding (Year)	3 years 9 months 18 days	4 years 3 months 18 days
Aggregate intrinsic value, options outstanding	$ 43,277	$ 17,283
Number of shares exercisable (in shares)	479	846
Aggregate intrinsic value, options exercisable	$ 11,729	$ 9,389
Weighted average remaining contractual life in years, options exercisable (Year)	3 years 2 months 12 days	3 years 3 months 18 days
Exercise Price 1 [Member]
Number of shares outstanding (in shares)	59	75
Weighted average remaining contractual life in years, options outstanding (Year)	1 year 6 months	1 year 9 months 18 days
Aggregate intrinsic value, options outstanding	$ 4,369	$ 3,933
Number of shares exercisable (in shares)	0	0
Aggregate intrinsic value, options exercisable	$ 0	$ 0
Exercise price (in dollars per share)		$ 0
Exercise Price 2 [Member]
Number of shares outstanding (in shares)	427	29
Weighted average remaining contractual life in years, options outstanding (Year)	2 years 6 months	3 months 18 days
Aggregate intrinsic value, options outstanding	$ 13,517	$ 924
Number of shares exercisable (in shares)	230	29
Aggregate intrinsic value, options exercisable	$ 7,295	$ 924
Exercise price (in dollars per share)	$ 42.87	$ 20.13
Weighted average remaining contractual life in years, options exercisable (Year)	2 years 6 months	3 months 18 days
Exercise Price 3 [Member]
Number of shares outstanding (in shares)	15	99
Weighted average remaining contractual life in years, options outstanding (Year)	3 years 10 months 24 days	4 months 24 days
Aggregate intrinsic value, options outstanding	$ 406	$ 2,897
Number of shares exercisable (in shares)	15	99
Aggregate intrinsic value, options exercisable	$ 406	$ 2,897
Exercise price (in dollars per share)	$ 47.46	$ 23.34
Weighted average remaining contractual life in years, options exercisable (Year)	3 years 10 months 24 days	4 months 24 days
Exercise Price 4 [Member]
Number of shares outstanding (in shares)	8	15
Weighted average remaining contractual life in years, options outstanding (Year)	5 years	4 years 1 month 6 days
Aggregate intrinsic value, options outstanding	$ 182	$ 257
Number of shares exercisable (in shares)	0	15
Aggregate intrinsic value, options exercisable	$ 0	$ 257
Exercise price (in dollars per share)	$ 51.71	$ 35.15
Weighted average remaining contractual life in years, options exercisable (Year)		4 years 1 month 6 days
Exercise Price 5 [Member]
Number of shares outstanding (in shares)	35	15
Weighted average remaining contractual life in years, options outstanding (Year)	4 years 10 months 24 days	3 years 9 months 18 days
Aggregate intrinsic value, options outstanding	$ 756	$ 211
Number of shares exercisable (in shares)	15	15
Aggregate intrinsic value, options exercisable	$ 329	$ 211
Exercise price (in dollars per share)	$ 53.16	$ 38.24
Weighted average remaining contractual life in years, options exercisable (Year)	4 years 10 months 24 days	3 years 9 months 18 days
Exercise Price 6 [Member]
Number of shares outstanding (in shares)	783	942
Weighted average remaining contractual life in years, options outstanding (Year)	4 years 6 months	3 years 6 months
Aggregate intrinsic value, options outstanding	$ 16,498	$ 8,879
Number of shares exercisable (in shares)	0	521
Aggregate intrinsic value, options exercisable	$ 0	$ 4,918
Exercise price (in dollars per share)	$ 53.44	$ 42.87
Weighted average remaining contractual life in years, options exercisable (Year)		3 years 6 months
Exercise Price 7 [Member]
Number of shares outstanding (in shares)	296	38
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	$ 5,724	$ 182
Number of shares exercisable (in shares)	131	38
Aggregate intrinsic value, options exercisable	$ 2,527	$ 182
Exercise price (in dollars per share)	$ 55.16	$ 47.46
Weighted average remaining contractual life in years, options exercisable (Year)	3 years 10 months 24 days	4 years 10 months 24 days
Exercise Price 8 [Member]
Number of shares outstanding (in shares)	30	35
Weighted average remaining contractual life in years, options outstanding (Year)	4 years 7 months 6 days	5 years 10 months 24 days
Aggregate intrinsic value, options outstanding	$ 497	$ 0
Number of shares exercisable (in shares)	30	0
Aggregate intrinsic value, options exercisable	$ 497	$ 0
Exercise price (in dollars per share)	$ 57.97	$ 53.16
Weighted average remaining contractual life in years, options exercisable (Year)	4 years 7 months 6 days
Exercise Price 9 [Member]
Number of shares outstanding (in shares)	12	828
Weighted average remaining contractual life in years, options outstanding (Year)	2 years 6 months	5 years 6 months
Aggregate intrinsic value, options outstanding	$ 187	$ 0
Number of shares exercisable (in shares)	6	0
Aggregate intrinsic value, options exercisable	$ 94	$ 0
Exercise price (in dollars per share)	$ 58.79	$ 53.44
Weighted average remaining contractual life in years, options exercisable (Year)	2 years 6 months
Exercise Price 10 [Member]
Number of shares outstanding (in shares)	98	296
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	$ 1,094	$ 0
Number of shares exercisable (in shares)	52	66
Aggregate intrinsic value, options exercisable	$ 581	$ 0
Exercise price (in dollars per share)	$ 63.35	$ 55.16
Weighted average remaining contractual life in years, options exercisable (Year)	3 years 10 months 24 days	4 years 10 months 24 days
Exercise Price 11 [Member]
Number of shares outstanding (in shares)	4	30
Weighted average remaining contractual life in years, options outstanding (Year)	5 years 7 months 6 days	5 years 7 months 6 days
Aggregate intrinsic value, options outstanding	$ 11	$ 0
Number of shares exercisable (in shares)	0	30
Aggregate intrinsic value, options exercisable	$ 0	$ 0
Exercise price (in dollars per share)	$ 71.71	$ 57.97
Weighted average remaining contractual life in years, options exercisable (Year)		5 years 7 months 6 days
Exercise Price 12 [Member]
Number of shares outstanding (in shares)	15	16
Weighted average remaining contractual life in years, options outstanding (Year)	5 years 8 months 12 days	3 years 6 months
Aggregate intrinsic value, options outstanding	$ 36	$ 0
Number of shares exercisable (in shares)	0	0
Aggregate intrinsic value, options exercisable	$ 0	$ 0
Exercise price (in dollars per share)	$ 72.14	$ 58.79
Exercise Price 13 [Member]
Number of shares outstanding (in shares)	10	109
Weighted average remaining contractual life in years, options outstanding (Year)	5 years 10 months 24 days	4 years 10 months 24 days
Aggregate intrinsic value, options outstanding	$ 0	$ 0
Number of shares exercisable (in shares)	0	33
Aggregate intrinsic value, options exercisable	$ 0	$ 0
Exercise price (in dollars per share)	$ 76.43	$ 63.35
Weighted average remaining contractual life in years, options exercisable (Year)		4 years 10 months 24 days