Note 5 - Loans and Allowance for Loan Losses - Troubled Debt Restructurings, Excluding Loans Acquired, Segregated by Class of Loans (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016	Sep. 30, 2017 USD ($)	Sep. 30, 2016	Dec. 31, 2016 USD ($)
Troubled debt, number	1	21	13	67
Commercial Real Estate Portfolio Segment [Member]
Troubled debt, number		15	3	49
Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member]
Troubled debt, number		13	1	22
Commercial Real Estate Portfolio Segment [Member] | Commercial Loans [Member]
Troubled debt, number	1
Commercial Portfolio Segment [Member]
Troubled debt, number	1	5	10	16
Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Troubled debt, number		5	10	16
Consumer Portfolio Segment [Member]
Troubled debt, number		1		2
Consumer Portfolio Segment [Member] | Other Loans [Member]
Troubled debt, number		1		2
Loans, Excluding Acquired Loans [Member]
Troubled debt, number			40		79
Troubled debt, balance	$ 17,383		$ 17,383		$ 14,174
Loans, Excluding Acquired Loans [Member] | Commercial Real Estate Portfolio Segment [Member]
Troubled debt, number			27		58
Troubled debt, balance	14,443		$ 14,443		$ 12,091
Loans, Excluding Acquired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Troubled debt, number			1		1
Troubled debt, balance	432		$ 432		$ 18
Loans, Excluding Acquired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member]
Troubled debt, number			18		32
Troubled debt, balance	982		$ 982		$ 2,245
Loans, Excluding Acquired Loans [Member] | Commercial Real Estate Portfolio Segment [Member] | Other Loans [Member]
Troubled debt, number			8		25
Troubled debt, balance	13,029		$ 13,029		$ 9,828
Loans, Excluding Acquired Loans [Member] | Commercial Portfolio Segment [Member]
Troubled debt, number			13		20
Troubled debt, balance	2,940		$ 2,940		$ 2,080
Loans, Excluding Acquired Loans [Member] | Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Troubled debt, number			13		20
Troubled debt, balance	2,940		$ 2,940		$ 2,080
Loans, Excluding Acquired Loans [Member] | Consumer Portfolio Segment [Member]
Troubled debt, number					1
Troubled debt, balance					$ 3
Loans, Excluding Acquired Loans [Member] | Consumer Portfolio Segment [Member] | Other Loans [Member]
Troubled debt, number					1
Troubled debt, balance					$ 3
Loans, Excluding Acquired Loans [Member] | Performing Financial Instruments [Member]
Troubled debt, number			16		41
Troubled debt, balance	9,212		$ 9,212		$ 10,998
Loans, Excluding Acquired Loans [Member] | Performing Financial Instruments [Member] | Commercial Real Estate Portfolio Segment [Member]
Troubled debt, number			9		26
Troubled debt, balance	7,021		$ 7,021		$ 9,215
Loans, Excluding Acquired Loans [Member] | Performing Financial Instruments [Member] | Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Troubled debt, number
Troubled debt, balance
Loans, Excluding Acquired Loans [Member] | Performing Financial Instruments [Member] | Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member]
Troubled debt, number			4		3
Troubled debt, balance	144		$ 144		$ 167
Loans, Excluding Acquired Loans [Member] | Performing Financial Instruments [Member] | Commercial Real Estate Portfolio Segment [Member] | Other Loans [Member]
Troubled debt, number			5		23
Troubled debt, balance	6,877		$ 6,877		$ 9,048
Loans, Excluding Acquired Loans [Member] | Performing Financial Instruments [Member] | Commercial Portfolio Segment [Member]
Troubled debt, number			7		15
Troubled debt, balance	2,191		$ 2,191		$ 1,783
Loans, Excluding Acquired Loans [Member] | Performing Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Troubled debt, number			7		15
Troubled debt, balance	2,191		$ 2,191		$ 1,783
Loans, Excluding Acquired Loans [Member] | Performing Financial Instruments [Member] | Consumer Portfolio Segment [Member]
Troubled debt, number
Troubled debt, balance
Loans, Excluding Acquired Loans [Member] | Performing Financial Instruments [Member] | Consumer Portfolio Segment [Member] | Other Loans [Member]
Troubled debt, number
Troubled debt, balance
Loans, Excluding Acquired Loans [Member] | Nonperforming Financial Instruments [Member]
Troubled debt, number			24		38
Troubled debt, balance	8,171		$ 8,171		$ 3,176
Loans, Excluding Acquired Loans [Member] | Nonperforming Financial Instruments [Member] | Commercial Real Estate Portfolio Segment [Member]
Troubled debt, number			18		32
Troubled debt, balance	7,422		$ 7,422		$ 2,876
Loans, Excluding Acquired Loans [Member] | Nonperforming Financial Instruments [Member] | Commercial Real Estate Portfolio Segment [Member] | Construction Loans [Member]
Troubled debt, number			1		1
Troubled debt, balance	432		$ 432		$ 18
Loans, Excluding Acquired Loans [Member] | Nonperforming Financial Instruments [Member] | Commercial Real Estate Portfolio Segment [Member] | Single Family Residential Loans [Member]
Troubled debt, number			14		29
Troubled debt, balance	838		$ 838		$ 2,078
Loans, Excluding Acquired Loans [Member] | Nonperforming Financial Instruments [Member] | Commercial Real Estate Portfolio Segment [Member] | Other Loans [Member]
Troubled debt, number			3		2
Troubled debt, balance	6,152		$ 6,152		$ 780
Loans, Excluding Acquired Loans [Member] | Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member]
Troubled debt, number			6		5
Troubled debt, balance	749		$ 749		$ 297
Loans, Excluding Acquired Loans [Member] | Nonperforming Financial Instruments [Member] | Commercial Portfolio Segment [Member] | Commercial Loans [Member]
Troubled debt, number			6		5
Troubled debt, balance	$ 749		$ 749		$ 297
Loans, Excluding Acquired Loans [Member] | Nonperforming Financial Instruments [Member] | Consumer Portfolio Segment [Member]
Troubled debt, number					1
Troubled debt, balance					$ 3
Loans, Excluding Acquired Loans [Member] | Nonperforming Financial Instruments [Member] | Consumer Portfolio Segment [Member] | Other Loans [Member]
Troubled debt, number					1
Troubled debt, balance					$ 3