Note 4 - Stockholders' Equity - Option Activity (Details) - $ / shares	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Outstanding (in shares)	136,105
Outstanding, weighted average exercise price (in dollars per share)	$ 40.07
Granted (in shares)	0	0
Granted, weighted average exercise price (in dollars per share)
Vested (in shares)
Vested, weighted average exercise price (in dollars per share)
Forfeited, canceled (in shares)	(39,708)
Forfeited, canceled, weighted average exercise price (in dollars per share)	$ 52.79
Outstanding (in shares)	96,397
Outstanding, weighted average exercise price (in dollars per share)	$ 34.83