Note 10 - Business Combination (Details Textual) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Oct. 04, 2018	Mar. 31, 2019
Subsequent Event [Member] | Core Deposits [Member] | Merchants Holding Company [Member]
Finite-Lived Intangible Assets, Gross, Total	$ 151.0
Merchants Holding Company [Member] | Subsequent Event [Member]
Share Price	$ 11.80
Maximum Percentage Decline of Core Deposits to Avoid Adjustments to Merger Consideration	7.50%
Minimum Percentage Decline in Core Deposit Balances to Terminate Merger Agreement	15.00%
Merchants Holding Company [Member] | Scenario, Forecast [Member]
Business Acquisition, Equity Interest Issued or Issuable, Shares Available for Issuance Upon Conversion of Acquiree Stock		3.8703
Business Acquisition, Share Price		$ 48.43
Business Acquisition, Equity Interest Issued or Issuable, Shares Available for Issuance Upon Conversion of Acquiree Stock if a Combination of Stock and Cash		2.3223
Business Acquisition, Share Price if Combination of Shares and Cash are Given		$ 19.37
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares		1,834,173
Business Combination, Maximum Amount of Cash to Be Paid in Lieu of Shares		$ 15.3
Business Combination, Consideration Transferred, Total		$ 37.0
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners		10.00%