Note 7 - Stock-based Compensation - Restricted Stock Units (Details)	9 Months Ended
	Sep. 30, 2023 $ / shares shares
Time-based Restricted Stock Units [Member]
Balance (in shares) | shares	202,059
Balance, weighted-average grant date fair value (in dollars per share) | $ / shares	$ 33.29
Granted (in shares) | shares	85,120
Granted, weighted-average grant date fair value (in dollars per share) | $ / shares	$ 37.97
Vested (in shares) | shares	(2,381)
Vested, weighted-average grant date fair value (in dollars per share) | $ / shares	$ 35.19
Forfeited (in shares) | shares	(1,774)
Forfeited, weighted-average grant date fair value (in dollars per share) | $ / shares	$ 42.52
Balance (in shares) | shares	283,024
Balance, weighted-average grant date fair value (in dollars per share) | $ / shares	$ 34.62
Performance-based Restricted Stock Units [Member]
Balance (in shares) | shares	362,965
Balance, weighted-average grant date fair value (in dollars per share) | $ / shares	$ 31.56
Granted (in shares) | shares	123,504
Granted, weighted-average grant date fair value (in dollars per share) | $ / shares	$ 38.41
Vested (in shares) | shares	(136,808)
Vested, weighted-average grant date fair value (in dollars per share) | $ / shares	$ 34.21
Forfeited (in shares) | shares	0
Forfeited, weighted-average grant date fair value (in dollars per share) | $ / shares	$ 0
Balance (in shares) | shares	349,661
Balance, weighted-average grant date fair value (in dollars per share) | $ / shares	$ 32.94