Note 4 - Investments - Maturities of Investment Portfolio (Details) - USD ($)
$ in Thousands
Dec. 31, 2016
Dec. 31, 2015
Securities available-for-sale:    
Available-for-sale Securities, Amortized Cost Basis $ 404,482 $ 384,031
Total securities available-for-sale 402,501 384,934
Securities held-to-maturity:    
Due after ten years 6,730  
Due after ten years 6,817  
Total securities held-to-maturity 91,752 108,157
Total securities held-to-maturity 92,828 107,629
US Government Agencies Debt Securities [Member]    
Securities available-for-sale:    
Due under one year 0  
Due under one year 0  
Available-for-sale Securities, Amortized Cost Basis 0 503
Total securities available-for-sale 0 514
US States and Political Subdivisions Debt Securities [Member]    
Securities available-for-sale:    
Due after five years through ten years 5,823  
Due after five years through ten years 6,023  
Due after ten years 6,908  
Due after ten years 7,296  
Due after ten years 6,908  
Available-for-sale Securities, Amortized Cost Basis 12,731 14,049
Total securities available-for-sale 13,319 14,796
Residential Agency Pass-Through Securities [Member]    
Securities available-for-sale:    
Due after five years through ten years 17,320  
Due after five years through ten years 17,789  
Due after ten years 176,855  
Due after ten years 174,976  
Due after ten years 176,855  
Available-for-sale Securities, Amortized Cost Basis 194,175 130,041
Total securities available-for-sale 192,765 131,460
Securities held-to-maturity:    
Due after ten years 34,063  
Due after ten years 34,553  
Total securities held-to-maturity 34,063 41,012
Total securities held-to-maturity 34,553 41,790
Collateralized Mortgage Obligations [Member]    
Securities available-for-sale:    
Due after five years through ten years 14,723  
Due after five years through ten years 14,742  
Due after ten years 79,257  
Due after ten years 79,668  
Due after ten years 79,257  
Available-for-sale Securities, Amortized Cost Basis 93,980 151,928
Total securities available-for-sale 94,410 151,631
Securities held-to-maturity:    
Total securities held-to-maturity 6,730 7,723
Total securities held-to-maturity 6,817 7,792
Commercial Mortgage Backed Securities [Member]    
Securities available-for-sale:    
Due after ten years 8,436  
Due after ten years 8,200  
Due after one year through five years 7,476  
Due after one year through five years 7,297  
Due after ten years 8,436  
Available-for-sale Securities, Amortized Cost Basis 15,912 4,856
Total securities available-for-sale 15,497 4,756
Securities held-to-maturity:    
Due after five years through ten years 46,851  
Due after five years through ten years 47,377  
Total securities held-to-maturity 46,851 54,028
Total securities held-to-maturity 47,377 52,661
Asset-backed Securities [Member]    
Securities available-for-sale:    
Due after five years through ten years 23,304  
Due after five years through ten years 22,755  
Due after ten years 61,651  
Due after ten years 61,196  
Due after ten years 61,651  
Available-for-sale Securities, Amortized Cost Basis 84,955 79,941
Total securities available-for-sale 83,951 79,120
Securities held-to-maturity:    
Due after ten years 4,108  
Due after ten years 4,081  
Total securities held-to-maturity 4,108 5,394
Total securities held-to-maturity 4,081 5,386
Corporate Debt Securities [Member]    
Securities available-for-sale:    
Due after ten years 1,479  
Due after ten years 1,320  
Due after ten years 1,479  
Available-for-sale Securities, Amortized Cost Basis 1,479 1,463
Total securities available-for-sale 1,320 1,500
Equity Securities [Member]    
Securities available-for-sale:    
Due after ten years 1,250  
Due after ten years 1,239  
Due after ten years 1,250  
Available-for-sale Securities, Amortized Cost Basis 1,250 1,250
Total securities available-for-sale $ 1,239 $ 1,157