Note 11 - Assets and Liabilities Measured and Reported at Fair Value - Assets Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Securities available-for-sale	$ 429,184	$ 470,738
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	429,184	470,738
Fair Value, Recurring [Member]
Securities available-for-sale	0	49,897
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	0	49,897
Interest rate swaps	0	0
Total assets	0	49,897
Interest rate swaps	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	429,184	420,841
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	429,184	420,841
Interest rate swaps	9,433	2,696
Total assets	438,617	423,537
Interest rate swaps	9,708	2,767
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	0	0
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	0	0
Interest rate swaps	0	0
Total assets	0	0
Interest rate swaps	0	0
Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	429,184	470,738
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	429,184	470,738
Interest rate swaps	9,433	2,696
Total assets	438,617	473,434
Interest rate swaps	9,708	2,767
US Government-sponsored Enterprises Debt Securities [Member]
Securities available-for-sale	141,881	209,944
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	141,881	209,944
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Recurring [Member]
Securities available-for-sale	0	0
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	0	0
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	141,881	209,944
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	141,881	209,944
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	0	0
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	0	0
US Government-sponsored Enterprises Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	141,881	209,944
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	141,881	209,944
US Treasury and Government [Member] | Fair Value, Recurring [Member]
Securities available-for-sale		49,897
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively		49,897
US Treasury and Government [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale		0
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively		0
US Treasury and Government [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale		0
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively		0
US Treasury and Government [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale		49,897
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively		49,897
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Securities available-for-sale	279,452	193,861
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	279,452	193,861
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Recurring [Member]
Securities available-for-sale	0	0
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	0	0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	279,452	193,861
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	279,452	193,861
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	0	0
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	0	0
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	279,452	193,861
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	279,452	193,861
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale	7,851	17,036
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	7,851	17,036
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member]
Securities available-for-sale	0	0
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	0	0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Securities available-for-sale	7,851	17,036
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	7,851	17,036
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Securities available-for-sale	0	0
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	0	0
US States and Political Subdivisions Debt Securities [Member] | Fair Value, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Securities available-for-sale	7,851	17,036
Available for sale debt securities (amortized cost of $416,767) in 2020 and $469,313 in 2019, respectively	$ 7,851	$ 17,036