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Note 8 - Loans - Allowance for Loan Losses by Portfolio Segment and Based on Impairment Method (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Loans individually evaluated for impairment, allowance |  | $ 6,429
Loans individually evaluated for impairment, balance |  | 95,405
Loans collectively evaluated for impairment, allowance |  | 160,109
Loans collectively evaluated for impairment, balance |  | 15,548,991
Loans, allowance | $ 147,264 | 166,538
Loans | 15,651,848 | 15,644,396
Commercial Portfolio Segment [Member] |  |
Loans individually evaluated for impairment, allowance |  | 1,030
Loans individually evaluated for impairment, balance |  | 27,070
Loans collectively evaluated for impairment, allowance |  | 67,712
Loans collectively evaluated for impairment, balance |  | 2,809,763
Loans, allowance |  | 68,742
Loans | 2,890,693 | 2,836,833
Real Estate Construction Portfolio Segment [Member] |  |
Loans individually evaluated for impairment, allowance |  | 0
Loans individually evaluated for impairment, balance |  | 4,286
Loans collectively evaluated for impairment, allowance |  | 30,854
Loans collectively evaluated for impairment, balance |  | 675,206
Loans, allowance |  | 30,854
Loans | 677,816 | 679,492
Commercial Real Estate Portfolio Segment [Member] |  |
Loans individually evaluated for impairment, allowance |  | 5,254
Loans individually evaluated for impairment, balance |  | 53,289
Loans collectively evaluated for impairment, allowance |  | 43,951
Loans collectively evaluated for impairment, balance |  | 7,501,738
Loans, allowance |  | 49,205
Loans | 7,549,522 | 7,555,027
Residential Mortgage and Equity Lines Portfolio Segment [Member] |  |
Loans individually evaluated for impairment, allowance |  | 145
Loans individually evaluated for impairment, balance |  | 10,760
Loans collectively evaluated for impairment, allowance |  | 17,592
Loans collectively evaluated for impairment, balance |  | 4,559,184
Loans, allowance |  | 17,737
Loans | $ 4,530,521 | 4,569,944
Consumer Portfolio Segment [Member] |  |
Loans individually evaluated for impairment, allowance |  | 0
Loans individually evaluated for impairment, balance |  | 0
Loans collectively evaluated for impairment, allowance |  | 0
Loans collectively evaluated for impairment, balance |  | 3,100
Loans, allowance |  | 0
Loans |  | $ 3,100

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- Definition The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 + Details
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- Definition Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 + Details
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- Definition The balance of financing receivables that were collectively evaluated for impairment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 + Details
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- Definition The balance of financing receivables that were individually evaluated for impairment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 + Details
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- Definition 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (b)(1)(ii) -URI http://asc.fasb.org/extlink&oid=121614798&loc=d3e15032-111544 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SAB Topic 6.L.1) -URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707 + Details
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- Definition 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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522 + Details
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