Note 10 - Fair Value of Financial Instruments - Fair Value Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Securities available for sale, fair value	$ 729,261	$ 738,354
Fair Value, Measurements, Recurring [Member]
Total assets	751,115	745,742
Liabilities:
Financial and Nonfinancial Liabilities, Fair Value Disclosure	40,345	40,744
Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Total assets	11,451	11,575
Liabilities:
Financial and Nonfinancial Liabilities, Fair Value Disclosure
Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Total assets	738,502	733,057
Liabilities:
Financial and Nonfinancial Liabilities, Fair Value Disclosure	1,653	3,758
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Total assets	1,162	1,110
Liabilities:
Financial and Nonfinancial Liabilities, Fair Value Disclosure	38,692	36,986
Collateralized Mortgage Backed Securities [Member]
Securities available for sale, fair value	512,781	509,650
Collateralized Mortgage Backed Securities [Member] \| Fair Value, Measurements, Recurring [Member]
Securities available for sale, fair value	512,781	509,650
Collateralized Mortgage Backed Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Securities available for sale, fair value
Collateralized Mortgage Backed Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Securities available for sale, fair value	512,781	509,650
Collateralized Mortgage Backed Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Securities available for sale, fair value
Other Securities [Member]
Securities available for sale, fair value	1,162	1,110
Other Securities [Member] \| Fair Value, Measurements, Recurring [Member]
Securities available for sale, fair value	216,480	228,704
Other Securities [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Securities available for sale, fair value	11,451	11,575
Other Securities [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Securities available for sale, fair value	203,867	216,019
Other Securities [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Securities available for sale, fair value	1,162	1,110
Interest Rate Swap [Member] \| Fair Value, Measurements, Recurring [Member]
Interest Rate Swaps, Net Amount	21,854	7,388
Liabilities:
Interest Rate Swaps, Net Amount	1,653	3,758
Interest Rate Swap [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Interest Rate Swaps, Net Amount
Liabilities:
Interest Rate Swaps, Net Amount
Interest Rate Swap [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Interest Rate Swaps, Net Amount	21,854	7,388
Liabilities:
Interest Rate Swaps, Net Amount	1,653	3,758
Interest Rate Swap [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Interest Rate Swaps, Net Amount
Liabilities:
Interest Rate Swaps, Net Amount
Junior Subordinated Debentures [Member] \| Fair Value, Measurements, Recurring [Member]
Liabilities:
Borrowings	38,692	36,986
Junior Subordinated Debentures [Member] \| Fair Value, Inputs, Level 1 [Member] \| Fair Value, Measurements, Recurring [Member]
Liabilities:
Borrowings
Junior Subordinated Debentures [Member] \| Fair Value, Inputs, Level 2 [Member] \| Fair Value, Measurements, Recurring [Member]
Liabilities:
Borrowings
Junior Subordinated Debentures [Member] \| Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Liabilities:
Borrowings	$ 38,692	$ 36,986

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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