Note 8 - Loans - Troubled Debt Restructuring (Details)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)
No. of Contracts	14	8	21	14
Pre-Modification Outstanding Recorded Investment	$ 23,479,000	$ 18,996,000	$ 52,638,000	$ 24,207,000
Post-Modification Outstanding Recorded Investment	23,174,000	18,996,000	52,333,000	24,207,000
Charge-offs	305,000		305,000
Special Reserve	$ 678,000	$ 208,000	$ 678,000	$ 208,000	$ 678,000
Commercial Portfolio Segment [Member]
No. of Contracts	8	7	13	11
Pre-Modification Outstanding Recorded Investment	$ 18,873,000	$ 18,258,000	$ 19,543,000	$ 23,102,000
Post-Modification Outstanding Recorded Investment	18,873,000	18,258,000	19,543,000	23,102,000
Charge-offs					2,100,000
Special Reserve	$ 636,000	$ 208,000	$ 636,000	$ 208,000	636,000
Commercial Real Estate Portfolio Segment [Member]
No. of Contracts	5	1	5	1
Pre-Modification Outstanding Recorded Investment	$ 4,123,000	$ 738,000	$ 4,123,000	$ 738,000
Post-Modification Outstanding Recorded Investment	3,818,000	738,000	3,818,000	738,000
Charge-offs	305,000		305,000
Special Reserve	10,000		$ 10,000		10,000
Real Estate Construction Portfolio Segment [Member]
No. of Contracts			2
Pre-Modification Outstanding Recorded Investment			$ 28,489,000
Post-Modification Outstanding Recorded Investment			28,489,000
Charge-offs
Special Reserve
Residential Mortgage and Equity Lines Portfolio Segment [Member]
No. of Contracts	1		1	2
Pre-Modification Outstanding Recorded Investment	$ 483,000		$ 483,000	$ 367,000
Post-Modification Outstanding Recorded Investment	483,000		483,000	367,000
Charge-offs
Special Reserve	$ 32,000		$ 32,000		$ 32,000