Note 13 - Equity Incentive Plan - Stock Options and SAR's Activity (Details)	12 Months Ended
	Dec. 31, 2018 $ / shares	Dec. 31, 2017 $ / shares
Options and SARs outstanding	1,327,200
Options and SAR's outstanding, Weighted Average Exercise Price Per Share (in dollars per share)	$ 42.06	$ 33.70
Options and SAR's Granted	199,970
Options and SAR's Granted, Weighted Average Exercise Price Per Share (in dollars per share)	$ 58.11
Options and SAR's Cancelled	(104,629)
Options and SAR's Cancelled, Weighted Average Exercise Price Per Share (in dollars per share)	$ 50.19
Options and SAR's Expired	(1,079)
Options and SAR's Expired, Weighted Average Exercise Price Per Share (in dollars per share)	$ 46.49
Options and SAR's Exercised	(284,548)
Options and SAR's Exercised, Weighted Average Exercise Price Per Share (in dollars per share)	$ 10.14
Options and SARs outstanding	1,136,914