Note 14 - Stock-based Compensation - Summary of Options Outstanding (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Options outstanding, shares (in shares)	785,529	1,163,381
Options outstanding, weighted average exercise price (in dollars per share)	$ 72.12	$ 71.24	$ 71.16
Options granted, shares (in shares)	102,124	53,316
Options granted, weighted average exercise price (in dollars per share)	$ 75.74	$ 77.89
Options exercised, shares (in shares)	(33,573)	(346,168)
Options exercised, weighted average exercise price (in dollars per share)	$ 62.46	$ 71.57
Options cancelled, shares (in shares)	(3,000)	(85,000)
Options cancelled, weighted average exercise price (in dollars per share)	$ 72.94	$ 72.94
Options outstanding, shares (in shares)	851,080	785,529
Options outstanding, aggregate intrinsic value	$ 66,000
Options exercisable, shares (in shares)	215,456
Options exercisable, weighted average exercise price (in dollars per share)	$ 68.35
Options exercisable, aggregate intrinsic value	$ 18,000