Note 11 - Fair Value of Financial Instruments - Fair Value Measured on a Recurring Basis (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Securities available for sale, fair value	$ 808,653,000	$ 822,655,000
Collateralized Mortgage Backed Securities [Member]
Securities available for sale, fair value	554,481,000	557,953,000
Other Securities [Member]
Securities available for sale, fair value	1,303,000	1,256,000
Fair Value, Recurring [Member]
Total assets	810,288,000	838,616,000
Financial and Nonfinancial Liabilities, Fair Value Disclosure	63,561,000	44,088,000
Fair Value, Recurring [Member] \| Collateralized Mortgage Backed Securities [Member]
Securities available for sale, fair value	554,481,000	557,953,000
Fair Value, Recurring [Member] \| Other Securities [Member]
Securities available for sale, fair value	254,172,000	264,702,000
Fair Value, Recurring [Member] \| Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount	1,635,000	15,961,000
Interest Rate Swaps, Net Amount	20,147,000	2,239,000
Fair Value, Recurring [Member] \| Junior Subordinated Debentures [Member]
Liabilities, Fair Value	43,414,000	41,849,000
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Total assets	12,042,000	11,586,000
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Collateralized Mortgage Backed Securities [Member]
Securities available for sale, fair value	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Other Securities [Member]
Securities available for sale, fair value	12,042,000	11,586,000
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount	0	0
Interest Rate Swaps, Net Amount	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Junior Subordinated Debentures [Member]
Liabilities, Fair Value	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Total assets	796,943,000	825,774,000
Financial and Nonfinancial Liabilities, Fair Value Disclosure	20,147,000	2,239,000
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Collateralized Mortgage Backed Securities [Member]
Securities available for sale, fair value	554,481,000	557,953,000
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Other Securities [Member]
Securities available for sale, fair value	240,827,000	251,860,000
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount	1,635,000	15,961,000
Interest Rate Swaps, Net Amount	20,147,000	2,239,000
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Junior Subordinated Debentures [Member]
Liabilities, Fair Value	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Total assets	1,303,000	1,256,000
Financial and Nonfinancial Liabilities, Fair Value Disclosure	43,414,000	41,849,000
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Collateralized Mortgage Backed Securities [Member]
Securities available for sale, fair value	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Other Securities [Member]
Securities available for sale, fair value	1,303,000	1,256,000
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Interest Rate Swap [Member]
Interest Rate Swaps, Net Amount	0	0
Interest Rate Swaps, Net Amount	0	0
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Junior Subordinated Debentures [Member]
Liabilities, Fair Value	$ 43,414,000	$ 41,849,000

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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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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