Note 6 - Loans and the Allowance for Loan Losses - Purchased Impaired Credits (Details) - USD ($)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Carrying amount, beginning balance	[1]	$ 1,776,000
Carrying amount, ending balance	[1]	696,000	$ 1,776,000
American Gateway Financial Corporation [Member]
Carrying amount, beginning balance		1,776,000	3,634,000
Payments received, net of discounts realized		(924,000)	(1,181,000)
Charge-offs		(667,000)	(352,000)
Transfer to other real estate			(325,000)
Purchased impaired credit participation interest sales proceeds, net of discount realized		511,000
Carrying amount, ending balance		$ 696,000	$ 1,776,000

[1] Purchased credit impaired loans are evaluated for impairment on an individual basis.