Note 1 - Nature of Operations - Summary of Significant Accounting Policies - (Details Textual) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Nov. 30, 2018	Jan. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets, Total			$ 2,273,835	$ 2,094,896
Loans and Leases Receivable, Net of Deferred Income, Total			1,710,265	1,528,469
Deposits, Total			1,782,010	1,733,934
Stockholders' Equity Attributable to Parent, Ending Balance			285,097	260,058	$ 179,935	$ 113,559
Debt Securities, Held-to-maturity, Total			0	0
Debt Securities, Trading, and Equity Securities, FV-NI, Total			$ 0	0
Open Tax Year			2016 2017 2018 2019
Advertising Expense			$ 1,500	$ 1,200	1,200
Operating Lease, Right-of-Use Asset			13,200
Other Liabilities [Member]
Operating Lease, Liability, Total			$ 13,242
Core Deposits [Member]
Finite-Lived Intangible Asset, Useful Life			10 years
Minden Bancorp [Member]
Assets, Total					317,400
Loans and Leases Receivable, Net of Deferred Income, Total					192,700
Deposits, Total					264,000
Stockholders' Equity Attributable to Parent, Ending Balance					$ 30,600
Richland State Bancorp [Member]
Assets, Total	$ 316,400
Loans and Leases Receivable, Net of Deferred Income, Total	190,800
Deposits, Total	290,000
Stockholders' Equity Attributable to Parent, Ending Balance	$ 25,400
Minden Bancorp [Member]
Payments to Acquire Businesses, Gross		$ 56,187
Business Acquisition, Price Paid Per Share of Common Stock of Acquired Entity		$ 23.20
Richland State Bancorp [Member]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares	1,679,559
Business Combination, Consideration Transferred, Total	$ 42,476