Note 6 - Loans and Related Allowance for Loan Loss - Nonperforming Assets (Details) - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Nonaccrual loans	$ 6,287,000	$ 3,281,000
Accruing loans past due 90 days or more	1,681,000	327,000
Nonperforming loans	2,800,000	3,600,000
Total Nonperforming Loans	935,888,000	912,872,000
Total Nonperforming Assets	$ 1,305,188,000	$ 1,281,301,000
Nonperforming Loans to Total Loans	1.06%	0.69%
Nonperforming Assets to Total Assets	0.78%	0.56%
Nonperforming Financial Instruments [Member]
Nonaccrual loans	$ 6,287,000	$ 3,281,000
Accruing loans past due 90 days or more	7,968,000	3,608,000
Nonperforming loans	1,934,000	2,705,000
Total Nonperforming Loans	9,902,000	6,313,000
Total Real Estate Owned	332,000	917,000
Total Nonperforming Assets	10,234,000	7,230,000
Residential Portfolio Segment [Member] \| Real Estate Sector [Member]
Nonaccrual loans	2,224,000	2,154,000
Total Nonperforming Loans	330,865,000	326,769,000
Residential Portfolio Segment [Member] \| Real Estate Sector [Member] \| Nonperforming Financial Instruments [Member]
Total Real Estate Owned	158,000	46,000
Commercial Portfolio Segment [Member] \| Real Estate Sector [Member]
Nonaccrual loans	3,149,000
Total Nonperforming Loans	317,182,000	307,064,000
Commercial Portfolio Segment [Member] \| Real Estate Sector [Member] \| Nonperforming Financial Instruments [Member]
Total Real Estate Owned	174,000	871,000
Commercial Portfolio Segment [Member] \| Commercial and Industrial Sector [Member]
Nonaccrual loans	809,000	1,044,000
Total Nonperforming Loans	93,850,000	91,463,000
Consumer Portfolio Segment [Member]
Nonaccrual loans	105,000	83,000
Total Nonperforming Loans	116,727,000	122,241,000
Originated Loans [Member]
Nonaccrual loans	5,108,000	1,866,000
Accruing loans past due 90 days or more	37,000	327,000
Nonperforming loans	2,200,000	2,100,000
Total Nonperforming Loans	756,867,000	721,591,000
Originated Loans [Member] \| Nonperforming Financial Instruments [Member]
Nonperforming loans	1,270,000	1,160,000
Originated Loans [Member] \| Residential Portfolio Segment [Member] \| Real Estate Sector [Member]
Nonaccrual loans	1,061,000	755,000
Accruing loans past due 90 days or more	20,000	324,000
Nonperforming loans	85,000	26,000
Total Nonperforming Loans	246,963,000	235,492,000
Originated Loans [Member] \| Commercial Portfolio Segment [Member] \| Real Estate Sector [Member]
Nonaccrual loans	3,149,000
Nonperforming loans	1,072,000	980,000
Total Nonperforming Loans	247,671,000	229,455,000
Originated Loans [Member] \| Commercial Portfolio Segment [Member] \| Commercial and Industrial Sector [Member]
Nonaccrual loans	793,000	1,028,000
Nonperforming loans	113,000	154,000
Total Nonperforming Loans	79,040,000	78,466,000
Originated Loans [Member] \| Consumer Portfolio Segment [Member]
Nonaccrual loans	105,000	83,000
Accruing loans past due 90 days or more	17,000	3,000
Total Nonperforming Loans	114,897,000	119,731,000
Acquired Loans [Member]
Nonaccrual loans	1,179,000	1,415,000
Accruing loans past due 90 days or more	1,644,000
Nonperforming loans	664,000	1,500,000
Total Nonperforming Loans	179,021,000	191,281,000
Acquired Loans [Member] \| Nonperforming Financial Instruments [Member]
Nonperforming loans	664,000	1,545,000
Acquired Loans [Member] \| Residential Portfolio Segment [Member] \| Real Estate Sector [Member]
Nonaccrual loans	1,163,000	1,399,000
Nonperforming loans	351,000	1,212,000
Total Nonperforming Loans	83,902,000	91,277,000
Acquired Loans [Member] \| Commercial Portfolio Segment [Member] \| Real Estate Sector [Member]
Nonaccrual loans
Accruing loans past due 90 days or more	1,644,000
Nonperforming loans	313,000	333,000
Total Nonperforming Loans	69,511,000	77,609,000
Acquired Loans [Member] \| Commercial Portfolio Segment [Member] \| Commercial and Industrial Sector [Member]
Nonaccrual loans	16,000	16,000
Total Nonperforming Loans	14,810,000	12,997,000
Acquired Loans [Member] \| Consumer Portfolio Segment [Member]
Nonaccrual loans
Total Nonperforming Loans	$ 1,830,000	$ 2,510,000

Reflects the percentage derived from dividing nonperforming assets by total assets.

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Amount of financing receivable modified as troubled debt restructuring.

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Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement.

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