Note 11 - Fair Value of Financial Instruments - Fair Value Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Assets:
Securities available for sale, fair value	$ 846,024	$ 822,655
Collateralized Mortgage Backed Securities [Member]
Assets:
Securities available for sale, fair value	579,185	557,953
Other Securities [Member]
Assets:
Securities available for sale, fair value	1,289	1,256
Fair Value, Recurring [Member]
Assets:
Total assets	852,498	838,616
Liabilities:
Financial and Nonfinancial Liabilities, Fair Value Disclosure	47,937	44,088
Fair Value, Recurring [Member] \| Collateralized Mortgage Backed Securities [Member]
Assets:
Securities available for sale, fair value	579,185	557,953
Fair Value, Recurring [Member] \| Other Securities [Member]
Assets:
Securities available for sale, fair value	266,839	264,702
Fair Value, Recurring [Member] \| Interest Rate Swap [Member]
Assets:
Interest rate swaps, assets	6,474	15,961
Liabilities:
Interest rate swaps, liabilities	4,996	2,239
Fair Value, Recurring [Member] \| Junior Subordinated Debentures [Member]
Liabilities:
Borrowings	42,941	41,849
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Assets:
Total assets	11,802	11,586
Liabilities:
Financial and Nonfinancial Liabilities, Fair Value Disclosure
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Collateralized Mortgage Backed Securities [Member]
Assets:
Securities available for sale, fair value
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Other Securities [Member]
Assets:
Securities available for sale, fair value	11,802	11,586
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Interest Rate Swap [Member]
Assets:
Interest rate swaps, assets
Liabilities:
Interest rate swaps, liabilities
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member] \| Junior Subordinated Debentures [Member]
Liabilities:
Borrowings
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Assets:
Total assets	839,407	825,774
Liabilities:
Financial and Nonfinancial Liabilities, Fair Value Disclosure	4,996	2,239
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Collateralized Mortgage Backed Securities [Member]
Assets:
Securities available for sale, fair value	579,185	557,953
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Other Securities [Member]
Assets:
Securities available for sale, fair value	253,748	251,860
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Rate Swap [Member]
Assets:
Interest rate swaps, assets	6,474	15,961
Liabilities:
Interest rate swaps, liabilities	4,996	2,239
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Junior Subordinated Debentures [Member]
Liabilities:
Borrowings
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Assets:
Total assets	1,289	1,256
Liabilities:
Financial and Nonfinancial Liabilities, Fair Value Disclosure	42,941	41,849
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Collateralized Mortgage Backed Securities [Member]
Assets:
Securities available for sale, fair value
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Other Securities [Member]
Assets:
Securities available for sale, fair value	1,289	1,256
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Interest Rate Swap [Member]
Assets:
Interest rate swaps, assets
Liabilities:
Interest rate swaps, liabilities
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member] \| Junior Subordinated Debentures [Member]
Liabilities:
Borrowings	$ 42,941	$ 41,849

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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-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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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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-Publisher FASB
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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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