Note 19 - Equity Incentive Plans - Restricted Stock Units (Details) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Time-based Restricted Stock Units [Member]
Balance (in shares)	284,493	221,738	152,476
Balance, weighted-average grant date fair value (in dollars per share)	$ 35.79	$ 32.72	$ 28.89
Granted (in shares)	108,925	141,810	87,781
Granted, weighted-average grant date fair value (in dollars per share)	$ 36.37	$ 43.30	$ 38.59
Vested (in shares)	(93,729)	(65,721)	(1,167)
Vested, weighted-average grant date fair value (in dollars per share)	$ 35.14	$ 41.59	$ 38.03
Forfeited (in shares)	(26,489)	(13,334)	(17,352)
Forfeited, weighted-average grant date fair value (in dollars per share)	$ 39.34	$ 35.96	$ 33.10
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
Performance-based Restricted Stock Units [Member]
Balance (in shares)	265,659	339,872	574,943
Balance, weighted-average grant date fair value (in dollars per share)	$ 32.90	$ 33.52	$ 28.96
Granted (in shares)	124,586	55,455	159,264
Granted, weighted-average grant date fair value (in dollars per share)	$ 36.37	$ 39.46	$ 40.36
Vested (in shares)	(92,501)	(121,336)	(394,335)
Vested, weighted-average grant date fair value (in dollars per share)	$ 38.36	$ 37.87	$ 39.96
Forfeited (in shares)	0	(8,332)	0
Forfeited, weighted-average grant date fair value (in dollars per share)	$ 0	$ 0.30	$ 0
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