Note 7 - Loans and the Allowance for Loan Losses - (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Loans and Leases Receivable, Deferred Income, Total	$ 1,700,000		$ 1,300,000
Loans and Leases Receivable Reclassified from Overdraft	858,000		129,000
Loans Receivable, Unpaid Principal Balance	147,000,000		82,400,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net	10,704,000	[1]	696,000	[1]	$ 1,776,000
Loans and Leases Receivable, Net of Deferred Income, Total	1,528,469,000		975,284,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing	1,876,000		132,000
Financing Receivable, Recorded Investment, Nonaccrual Status	11,691,000		12,535,000
Impaired Financing Receivable, Interest Income, Accrual Method, Total	254,000		247,000
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	79,000		3,300,000
Minden Bancorp and Richland State Bancorp [Member] | Performing Financial Instruments [Member]
Loans and Leases Receivable, Deferred Income, Total	3,200,000
Loans Receivable, Fair Value Disclosure	334,800,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net	10,700,000
Loans and Leases Receivable, Net of Deferred Income, Total	$ 327,300,000
American Gateway Financial Corporation [Member] | Performing Financial Instruments [Member]
Loans and Leases Receivable, Deferred Income, Total			1,800,000
Loans Receivable, Fair Value Disclosure			46,100,000
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Carrying Amount, Net			696,000
Loans and Leases Receivable, Net of Deferred Income, Total			$ 47,200,000

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