Note 3 - Mergers and Acquisitions - (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	Jun. 04, 2018	Jan. 01, 2018	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Assets, Total			$ 1,649,207	$ 1,321,256
Loans and Leases Receivable, Net of Deferred Income, Total			1,234,031	975,284
Deposits, Total			1,329,493	1,055,533
Stockholders' Equity Attributable to Parent, Ending Balance			$ 210,629	179,935	$ 118,813	$ 113,559
Minden Bancorp [Member]
Assets, Total				317,100
Loans and Leases Receivable, Net of Deferred Income, Total				192,700
Deposits, Total				264,000
Stockholders' Equity Attributable to Parent, Ending Balance				$ 30,200
Minden Bancorp [Member]
Payments to Acquire Businesses, Gross		$ 56,187
Business Acquisition, Price Paid Per Share of Common Stock of Acquired Entity		$ 23.20
RSBI [Member]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares	1,207,500
Business Acquisition, Share Price	$ 24
Business Combination, Consideration Transferred, Total	$ 29,000
Business Combination, Underwriting Discount and Commission	$ 1,700