Note 8 - Loans - Allowance for Loan Losses by Portfolio Segment and Based on Impairment Method (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Loans individually evaluated for impairment, allowance	$ 1,414	$ 3,802
Loans individually evaluated for impairment, balance	119,631	106,886
Loans collectively evaluated for impairment, allowance	121,141	118,589
Loans collectively evaluated for impairment, balance	14,157,791	13,888,902
Loans, allowance	122,555	122,391
Loans	14,277,422	13,995,788
Commercial Portfolio Segment [Member]
Loans individually evaluated for impairment, allowance	498	1,837
Loans individually evaluated for impairment, balance	43,159	36,938
Loans collectively evaluated for impairment, allowance	54,252	53,141
Loans collectively evaluated for impairment, balance	2,693,036	2,705,027
Loans, allowance	54,750	54,978
Loans	2,736,195	2,741,965
Real Estate Construction Portfolio Segment [Member]
Loans individually evaluated for impairment, allowance
Loans individually evaluated for impairment, balance	4,801	4,873
Loans collectively evaluated for impairment, allowance	20,723	19,626
Loans collectively evaluated for impairment, balance	562,988	576,581
Loans, allowance	20,723	19,626
Loans	567,789	581,454
Commercial Real Estate Portfolio Segment [Member]
Loans individually evaluated for impairment, allowance	667	877
Loans individually evaluated for impairment, balance	58,352	51,472
Loans collectively evaluated for impairment, allowance	32,406	32,610
Loans collectively evaluated for impairment, balance	6,830,546	6,672,728
Loans, allowance	33,073	33,487
Loans	6,888,898	6,724,200
Residential Mortgage and Equity Lines Portfolio Segment [Member]
Loans individually evaluated for impairment, allowance	249	1,088
Loans individually evaluated for impairment, balance	13,319	13,603
Loans collectively evaluated for impairment, allowance	13,726	13,194
Loans collectively evaluated for impairment, balance	4,063,588	3,930,217
Loans, allowance	13,975	14,282
Loans	4,076,907	3,943,820
Consumer Portfolio Segment [Member]
Loans individually evaluated for impairment, allowance
Loans individually evaluated for impairment, balance
Loans collectively evaluated for impairment, allowance	34	18
Loans collectively evaluated for impairment, balance	7,633	4,349
Loans, allowance	34	18
Loans	$ 7,633	$ 4,349

The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment.

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-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
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Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment.

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The balance of financing receivables that were collectively evaluated for impairment.

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The balance of financing receivables that were individually evaluated for impairment.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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