Note 3 - Mergers and Acquisitions - (Details Textual) - USD ($)				12 Months Ended
	Jun. 28, 2019	Nov. 30, 2018	Jan. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets, Total				$ 2,273,835,000	$ 2,094,896,000
Loans and Leases Receivable, Net of Deferred Income, Total				1,710,265,000	1,528,469,000
Deposits, Total				1,782,010,000	1,733,934,000
Stockholders' Equity Attributable to Parent, Ending Balance				285,097,000	$ 260,058,000	$ 179,935,000	$ 113,559,000
Gain (Loss) on Disposition of Business				(1,000,000)
Goodwill, Written off Related to Sale of Business Unit				$ 1,000,000
Minden Bancorp [Member]
Assets, Total						317,400,000
Loans and Leases Receivable, Net of Deferred Income, Total						192,700,000
Deposits, Total						264,000,000
Stockholders' Equity Attributable to Parent, Ending Balance						$ 30,600,000
Richland State Bancorp [Member]
Assets, Total		$ 316,400,000
Loans and Leases Receivable, Net of Deferred Income, Total		190,800,000
Deposits, Total		290,000,000
Stockholders' Equity Attributable to Parent, Ending Balance		$ 25,400,000
Minden Bancorp [Member]
Payments to Acquire Businesses, Gross			$ 56,187,000
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		$ 42,476,000
Gain (Loss) on Disposition of Business	$ 581,000
Goodwill, Written off Related to Sale of Business Unit	$ 1,300,000