Note 4 - Credit Quality - Loans Modified as Troubled Debt Restructurings (Details) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)
Total contracts			6		6
Pre-modification recorded investment			$ 1,190		$ 1,190
Post-modification recorded investment	[1]		$ 1,190		$ 1,190
Below Market Interest Rate [Member] | Single Family Owner Occupied [Member]
Total contracts			1		1
Pre-modification recorded investment			$ 241		$ 241
Post-modification recorded investment	[1]		$ 241		$ 241
Below Market Interest Rate and Extended Payment Term [Member] | Single Family Owner Occupied [Member]
Total contracts			5		5
Pre-modification recorded investment			$ 949		$ 949
Post-modification recorded investment	[1]		$ 949		$ 949

[1] Represents the loan balance immediately following modification