Note 7 - Loans and the Allowance for Loan Losses - (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
Loans and Leases Receivable, Deferred Income, Total	$ 3,000,000		$ 1,700,000
Loans and Leases Receivable Reclassified from Overdraft	276,000		858,000
Loans Receivable, Unpaid Principal Balance	129,700,000		147,000,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net	5,009,000	[1]	10,704,000	[1]	$ 696,000
Loans and Leases Receivable, Net of Deferred Income, Total	1,710,265,000		1,528,469,000
Financing Receivable, 90 Days or More Past Due, Still Accruing	72,000		1,876,000
Financing Receivable, Nonaccrual	8,977,000		11,691,000
Impaired Financing Receivable, Interest Income, Accrual Method, Total	292,000		254,000
Financing Receivable, Troubled Debt Restructuring, Subsequent Default	0		79,000
Minden Bancorp and Richland State Bancorp [Member] | Performing Financial Instruments [Member]
Loans and Leases Receivable, Deferred Income, Total	2,000,000
Loans Receivable, Fair Value Disclosure	180,000,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net	5,000,000
Loans and Leases Receivable, Net of Deferred Income, Total	$ 177,100,000
American Gateway Financial Corporation [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net			10,700,000
American Gateway Financial Corporation [Member] | Performing Financial Instruments [Member]
Loans and Leases Receivable, Deferred Income, Total			3,200,000
Loans Receivable, Fair Value Disclosure			334,800,000
Loans and Leases Receivable, Net of Deferred Income, Total			$ 327,300,000

[1] Purchased credit impaired loans are evaluated for impairment on an individual basis.