Note 18 - Equity Incentive Plans - Restricted Stock Units (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Time-based Restricted Stock Units [Member]
Balance (in shares)	273,200	284,493	221,738
Balance, weighted-average grant date fair value (in dollars per share)	$ 35.90	$ 35.79	$ 32.72
Granted (in shares)	110,495	108,925	141,810
Granted, weighted-average grant date fair value (in dollars per share)	$ 21.79	$ 36.37	$ 43.30
Vested (in shares)	(80,654)	(93,729)	(65,721)
Vested, weighted-average grant date fair value (in dollars per share)	$ 25.34	$ 35.14	$ 41.59
Forfeited (in shares)	(10,371)	(26,489)	(13,334)
Forfeited, weighted-average grant date fair value (in dollars per share)	$ 39.04	$ 39.34	$ 35.96
Balance (in shares)	292,670	273,200	284,493
Balance, weighted-average grant date fair value (in dollars per share)	$ 33.37	$ 35.90	$ 35.79
Performance-based Restricted Stock Units [Member]
Balance (in shares)	297,744	265,659	339,872
Balance, weighted-average grant date fair value (in dollars per share)	$ 32.65	$ 32.90	$ 33.52
Granted (in shares)	212,369	124,586	55,455
Granted, weighted-average grant date fair value (in dollars per share)	$ 22.96	$ 36.37	$ 39.46
Vested (in shares)	(193,240)	(92,501)	(121,336)
Vested, weighted-average grant date fair value (in dollars per share)	$ 21.68	$ 38.36	$ 37.87
Forfeited (in shares)	(14,071)	0	(8,332)
Forfeited, weighted-average grant date fair value (in dollars per share)	$ 39.08	$ 0	$ 29.61
Balance (in shares)	302,802	297,744	265,659
Balance, weighted-average grant date fair value (in dollars per share)	$ 32.55	$ 32.65	$ 32.90