Note 8 - Stock-based Compensation - RSU Stock-based Payment Awards (Details) - Restricted Stock Units (RSUs) [Member]	6 Months Ended
	Jun. 30, 2022 $ / shares shares
Unvested, shares (in shares) | shares	5,509
Unvested, Weighted-average grant date fair value (in dollars per share) | $ / shares	$ 34.78
Vested, shars (in shares) | shares	(837)	[1]
Vested, Weighted-average grant date fair value (in dollars per share) | $ / shares	$ 29.87
Unvested, shares (in shares) | shares	4,672
Unvested, Weighted-average grant date fair value (in dollars per share) | $ / shares	$ 35.66

[1] The RSUs vested during the three months ended March 31, 2022 were settled on a hybrid basis. The Company withheld 120 shares of common stock and, in lieu of delivering such shares, paid the RSU holder an amount in cash equal to the fair market value of such shares on vesting date, representing the holder's approximate tax liability associated with such vesting amount in cash equal to the fair market value of such shares on vesting date, representing the holder's approximate tax liability associated with such vesting.