Note 10 - Fair Value of Financial Instruments - Fair Value Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Securities available for sale, fair value	$ 761,032	$ 738,354
Collateralized Mortgage Backed Securities [Member]
Securities available for sale, fair value	528,119	509,650
Other Securities [Member]
Securities available for sale, fair value	1,205	1,110
Fair Value, Measurements, Recurring [Member]
Total assets	793,632	745,742
Financial and Nonfinancial Liabilities, Fair Value Disclosure	40,600	40,744
Fair Value, Measurements, Recurring [Member] \| Collateralized Mortgage Backed Securities [Member]
Securities available for sale, fair value	528,119	509,650
Fair Value, Measurements, Recurring [Member] \| Other Securities [Member]
Securities available for sale, fair value	232,913	228,704
Fair Value, Measurements, Recurring [Member] \| Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount	32,600	7,388
Interest Rate Swaps, Net Amount	449	3,758
Fair Value, Measurements, Recurring [Member] \| Junior Subordinated Debentures [Member]
Liabilities, Fair Value	40,151	36,986
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Total assets	11,405	11,575
Financial and Nonfinancial Liabilities, Fair Value Disclosure
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Collateralized Mortgage Backed Securities [Member]
Securities available for sale, fair value
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Other Securities [Member]
Securities available for sale, fair value	11,405	11,575
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount
Interest Rate Swaps, Net Amount
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Junior Subordinated Debentures [Member]
Liabilities, Fair Value
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Total assets	781,022	733,057
Financial and Nonfinancial Liabilities, Fair Value Disclosure	449	3,758
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Collateralized Mortgage Backed Securities [Member]
Securities available for sale, fair value	528,119	509,650
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Other Securities [Member]
Securities available for sale, fair value	220,303	216,019
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount	32,600	7,388
Interest Rate Swaps, Net Amount	449	3,758
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Junior Subordinated Debentures [Member]
Liabilities, Fair Value
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Total assets	1,205	1,110
Financial and Nonfinancial Liabilities, Fair Value Disclosure	40,151	36,986
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Collateralized Mortgage Backed Securities [Member]
Securities available for sale, fair value
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Other Securities [Member]
Securities available for sale, fair value	1,205	1,110
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount
Interest Rate Swaps, Net Amount
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Junior Subordinated Debentures [Member]
Liabilities, Fair Value	$ 40,151	$ 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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-SubTopic 10
-Section 50
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Fair value of financial and nonfinancial obligations.

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