Note 21 - Regulatory Matters - Capital and Leverage Ratios (Details) - USD ($)	Dec. 31, 2021	Dec. 31, 2020
Common Equity Tier 1 to Risk-Weighted Assets, Actual amount	$ 2,137,925,000	$ 2,059,056,000
Common Equity Tier 1 to Risk-Weighted Assets, Actual ratio	13.32%	13.83%
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required	$ 1,123,721,000	$ 1,041,911,000
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required, Ratio	7.00%	7.00%
Common Equity Tier 1 to Risk-Weighted Assets, Required to be Considered Well Capitalized	$ 1,043,455,000	$ 967,489,000
Common Equity Tier 1 to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	6.50%	6.50%
Tier 1 Capital to Risk-Weighted Assets, Actual amount	$ 2,137,925,000	$ 2,059,056,000
Tier 1 Capital to Risk-Weighted Assets, Actual ratio	0.1332	0.1383
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required	$ 1,364,519,000	$ 1,265,178,000
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required, Ratio	8.50%	8.50%
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized	$ 1,284,253,000	$ 1,190,755,000
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	0.08	0.0800
Total Capital to Risk-Weighted Assets, Actual amount	$ 2,281,182,000	$ 2,231,474,000
Total Capital to Risk-Weighted Assets, Actual ratio	0.1421	0.1499
Total Capital to Risk-Weighted Assets, Minimum Capital Required	$ 1,685,582,000	$ 1,562,866,000
Total Capital to Risk-Weighted Assets, Minimum Capital Required, Ratio	10.50%	10.50%
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized	$ 1,605,316,000	$ 1,488,444,000
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	0.10	0.1000
Leverage Ratio, Actual amount	$ 2,137,925,000	$ 2,059,056,000
Leverage Ratio, Actual ratio	0.1082	0.1119
Leverage Ratio, Minimum Capital Required	$ 790,430,000	$ 736,317,000
Leverage Ratio Minimum Capital Required, Ratio	0.0400	0.0400
Leverage Ratio, Required to be Considered Well Capitalized	$ 988,037,000	$ 920,396,000
Leverage Ratio Required to be Considered Well Capitalized, Ratio	0.05	0.0500
Bank [Member]
Common Equity Tier 1 to Risk-Weighted Assets, Actual amount	$ 2,056,601,000	$ 2,016,448,000
Common Equity Tier 1 to Risk-Weighted Assets, Actual ratio	12.80%	13.53%
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required	$ 1,124,381	$ 1,042,967
Common Equity Tier 1 to Risk-Weighted Assets, Minimum Capital Required, Ratio	7.00%	7.00%
Common Equity Tier 1 to Risk-Weighted Assets, Required to be Considered Well Capitalized	$ 1,044,068,000	$ 968,470,000
Common Equity Tier 1 to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	6.50%	6.50%
Tier 1 Capital to Risk-Weighted Assets, Actual amount	$ 2,056,601,000	$ 2,016,448,000
Tier 1 Capital to Risk-Weighted Assets, Actual ratio	0.1280	0.1353
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required	$ 1,365,320,000	$ 1,266,460,000
Tier 1 Capital to Risk-Weighted Assets, Minimum Capital Required, Ratio	8.50%	8.50%
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized	$ 1,285,007,000	$ 1,191,963,000
Tier 1 Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	0.0800	0.0800
Total Capital to Risk-Weighted Assets, Actual amount	$ 2,315,358,000	$ 2,304,366,000
Total Capital to Risk-Weighted Assets, Actual ratio	0.1441	0.1547
Total Capital to Risk-Weighted Assets, Minimum Capital Required	$ 1,686,572,000	$ 1,564,451,000
Total Capital to Risk-Weighted Assets, Minimum Capital Required, Ratio	10.50%	10.50%
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized	$ 1,606,259,000	$ 1,489,953,000
Total Capital to Risk-Weighted Assets, Required to be Considered Well Capitalized, Ratio	0.1000	0.1000
Leverage Ratio, Actual amount	$ 2,056,601,000	$ 2,016,448,000
Leverage Ratio, Actual ratio	0.1040	0.1094
Leverage Ratio, Minimum Capital Required	$ 791,226,000	$ 737,382,000
Leverage Ratio Minimum Capital Required, Ratio	0.0400	0.0400
Leverage Ratio, Required to be Considered Well Capitalized	$ 989,033,000	$ 921,727,000
Leverage Ratio Required to be Considered Well Capitalized, Ratio	0.0500	0.0500