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Note 4 - Loans and Allowance for Loan Losses - Activity in Allowance for Loan Losses and the Recorded Investments in Loans (Details) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Provision for loan losses | $ 1,750,000 | $ 1,100,000 | $ 2,950,000
Ending balance | 2,856,667,000 | 2,753,085,000 |
Originated Loan [Member] |  |  |
Beginning balance | 21,554,000 | 19,133,000 | 17,868,000
Provision for loan losses | 1,867,000 | 400,000 | 2,641,000
Charge-offs | (883,000) | (1,189,000) | (3,183,000)
Recoveries | 628,000 | 3,210,000 | 1,807,000
Ending balance | 23,166,000 | 21,554,000 | 19,133,000
Ending balance: individually evaluated for impairment | 1,397,000 | 688,000 | 1,867,000
Ending balance: collectively evaluated for impairment | 21,769,000 | 20,866,000 | 17,266,000
Ending balance | 2,614,725,000 | 2,452,446,000 | 2,169,957,000
Ending balance: individually evaluated for impairment | 11,365,000 | 18,882,000 | 8,787,000
Ending balance: collectively evaluated for impairment | 2,603,360,000 | 2,433,564,000 | 2,161,170,000
Acquired Loan [Member] |  |  |
Beginning balance | 826,000 | 368,000 | 93,000
Provision for loan losses | (117,000) | 700,000 | 309,000
Charge-offs | 0 | (261,000) | (52,000)
Recoveries | 14,000 | 19,000 | 18,000
Ending balance | 723,000 | 826,000 | 368,000
Ending balance | 241,942,000 | 300,639,000 |
Commercial Portfolio Segment [Member] |  |  |
Ending balance | 2,441,544,000 | 2,360,106,000 |
Commercial Portfolio Segment [Member] | Originated Loan [Member] |  |  |
Beginning balance | 19,442,000 | 16,456,000 | 16,026,000
Provision for loan losses | 1,521,000 | 826,000 | 1,148,000
Charge-offs | (455,000) | (428,000) | (2,292,000)
Recoveries | 326,000 | 2,588,000 | 1,574,000
Ending balance | 20,834,000 | 19,442,000 | 16,456,000
Ending balance: individually evaluated for impairment | 1,150,000 | 451,000 | 1,202,000
Ending balance: collectively evaluated for impairment | 19,684,000 | 18,991,000 | 15,254,000
Ending balance | 2,271,417,000 | 2,151,998,000 | 1,934,228,000
Ending balance: individually evaluated for impairment | 9,828,000 | 17,134,000 | 6,394,000
Ending balance: collectively evaluated for impairment | 2,261,589,000 | 2,134,864,000 | 1,927,834,000
Commercial Portfolio Segment [Member] | Acquired Loan [Member] |  |  |
Beginning balance | 177,000 | 291,000 | 75,000
Provision for loan losses | 57,000 | 132,000 | 210,000
Charge-offs | 0 | (246,000) | (12,000)
Recoveries | 2,000 | 0 | 18,000
Ending balance | 236,000 | 177,000 | 291,000
Ending balance | 170,127,000 | 208,108,000 |
Retail Portfolio Segment [Member] |  |  |
Ending balance | 415,123,000 | 392,979,000 |
Retail Portfolio Segment [Member] | Originated Loan [Member] |  |  |
Beginning balance | 2,068,000 | 2,584,000 | 1,882,000
Provision for loan losses | 320,000 | (377,000) | 1,360,000
Charge-offs | (428,000) | (761,000) | (891,000)
Recoveries | 302,000 | 622,000 | 233,000
Ending balance | 2,262,000 | 2,068,000 | 2,584,000
Ending balance: individually evaluated for impairment | 247,000 | 237,000 | 665,000
Ending balance: collectively evaluated for impairment | 2,015,000 | 1,831,000 | 1,919,000
Ending balance | 343,308,000 | 300,448,000 | 235,729,000
Ending balance: individually evaluated for impairment | 1,537,000 | 1,748,000 | 2,393,000
Ending balance: collectively evaluated for impairment | 341,771,000 | 298,700,000 | 233,336,000
Retail Portfolio Segment [Member] | Acquired Loan [Member] |  |  |
Beginning balance | 649,000 | 77,000 | 18,000
Provision for loan losses | (174,000) | 568,000 | 99,000
Charge-offs | 0 | (15,000) | (40,000)
Recoveries | 12,000 | 19,000 | 0
Ending balance | 487,000 | 649,000 | 77,000
Ending balance | 71,815,000 | 92,531,000 |
Unallocated Financing Receivables [Member] | Originated Loan [Member] |  |  |
Beginning balance | 44,000 | 93,000 | (40,000)
Provision for loan losses | 26,000 | (49,000) | 133,000
Charge-offs | 0 | 0 | 0
Recoveries | 0 | 0 | 0
Ending balance | 70,000 | 44,000 | 93,000
Ending balance: individually evaluated for impairment | 0 | 0 | 0
Ending balance: collectively evaluated for impairment | 70,000 | 44,000 | 93,000
Unallocated Financing Receivables [Member] | Acquired Loan [Member] |  |  |
Beginning balance | 0 | 0 | 0
Provision for loan losses | 0 | 0 | 0
Charge-offs | 0 | 0 | 0
Recoveries | 0 | 0 | 0
Ending balance | $ 0 | $ 0 | $ 0

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