Note 4 - Loans and Allowance for Credit Losses on Loans (Details Textual) Pure in Thousands		3 Months Ended				9 Months Ended
	Jan. 01, 2020 USD ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)
Loans and Leases Receivable, Deferred Expense Income			$ 12,000,000					$ 7,000,000
Loans and Leases Receivable, Collateral for Secured Borrowings			1,900,000,000					1,600,000,000
Loans and Leases Receivable, Allowance, Initial Allowance on Acquired Loans		$ 0				$ 1,635,000
Loans and Leases Receivable, Net Amount, Total	$ 8,200,000	0				8,221,000
Financing Receivable, Allowance for Credit Loss, Ending Balance	37,000,000
Provision for Loan and Lease Losses, Total		4,418,000	5,500,000	$ 5,500,000	$ 400,000	15,518,000	$ 1,000,000
Off-Balance Sheet, Credit Loss, Liability, Credit Loss Expense (Reversal)		550,000	1,500,000	375,000	$ 0	2,400,000	$ 0
Off-Balance Sheet, Credit Loss, Liability, Ending Balance	3,850,000	$ 6,000,000				$ 6,000,000		350,000	$ 3,900,000
Financing Receivable, Modifications, Number of Contracts		0			0	0	0
Financing Receivable, Troubled Debt Restructuring, Subsequent Default, Number of Contracts						0
Mortgage Loans in Process of Foreclosure, Amount		$ 40,000				$ 40,000		239,000
Loans and Leases Receivable, Net Amount, Total		3,421,980,000				3,421,980,000		2,818,225,000
Financial Asset Acquired with Credit Deterioration [Member]
Loans and Leases Receivable, Net Amount, Total								1,600,000
Commercial Real Estate Portfolio Segment [Member]
Loans and Leases Receivable, Allowance, Initial Allowance on Acquired Loans		0				1,502,000
Loans and Leases Receivable, Net Amount, Total		0				4,488,000
Provision for Loan and Lease Losses, Total		1,116,000				12,106,000
Impaired Financing Receivable, Related Allowance Increase (Decrease)			2,000,000
Consumer Portfolio Segment [Member]
Loans and Leases Receivable, Allowance, Initial Allowance on Acquired Loans		0				34,000
Loans and Leases Receivable, Net Amount, Total		0				264,000
Provision for Loan and Lease Losses, Total		57,000			$ 12,000	54,000	$ (184,000)
Financing Receivable, Overdraft Balance			506,000
COVID-19 [Member]
Provision for Loan and Lease Losses, Total		4,400,000	$ 4,600,000	$ 4,200,000
Transfer of Loans From Purchased Credit Impaired to Purchased Credit Deteriorated [Member]
Loans and Leases Receivable, Allowance, Initial Allowance on Acquired Loans	1,600,000
Loans and Leases Receivable, Net Amount, Total	$ 1,600,000
Directors and Executive Officers [Member]
Loans and Leases Receivable, Related Parties, Ending Balance		$ 44,000,000				$ 44,000,000		$ 43,000,000