Note 11 - Stock-based Compensation - Restricted Stock Activity (Details) - Restricted Stock [Member]	3 Months Ended
	Mar. 31, 2020 $ / shares shares
Outstanding, shares (in shares) | shares	712,496
Outstanding, grant date fair value (in dollars per share) | $ / shares	$ 23.66
Granted, shares (in shares) | shares	38,941
Granted, grant date fair value (in dollars per share) | $ / shares	$ 10.45
Vested, shares (in shares) | shares	(75,565)
Vested, grant date fair value (in dollars per share) | $ / shares	$ 23.84
Canceled or forfeited, shares (in shares) | shares	(23,199)
Canceled or forfeited, grant date fair value (in dollars per share) | $ / shares	$ 24.74
Outstanding, shares (in shares) | shares	652,673
Outstanding, grant date fair value (in dollars per share) | $ / shares	$ 22.82