Note 20 - Mergers and Acquisitions (Details Textual) - USD ($)			9 Months Ended	12 Months Ended
	Oct. 01, 2018	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Sep. 30, 2018	Sep. 29, 2017
Goodwill, Ending Balance				$ 19,448,000	$ 10,288,000
Amortization of Intangible Assets, Total				266,000	246,000
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months				176,000
Finite-Lived Intangible Assets, Amortization Expense, Year Two				164,000
Finite-Lived Intangible Assets, Amortization Expense, Year Three				154,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four				149,000
Finite-Lived Intangible Assets, Amortization Expense, Year Five				149,000
Finite-Lived Intangible Assets, Amortization Expense, after Year Five				631,000
Business Combination, Acquisition Related Costs				3,592,000	1,119,000
Business Combination, Bargain Purchase, Gain Recognized, Amount					1,316,000
Community First [Member]
Payments to Acquire Businesses, Gross	$ 2,429,000
Goodwill, Ending Balance	9,161,000			9,200,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	1,208,000
Business Acquisition, Goodwill, Expected Tax Deductible Amount	0
Business Combination, Acquired Receivable, Fair Value						$ 112,800,000
Business Combination, Loans Receivable, Credit Adjustment	1,700,000
Business Combination, Loans Receivable, Other Adjustment	441,000
Business Combination, Acquisition Related Costs				3,600,000
Community First [Member] | Employee Non-Compete and Severance Costs [Member]
Business Combination, Acquisition Related Costs				1,500,000
Community First [Member] | Professional Fees [Member]
Business Combination, Acquisition Related Costs				531,000
Community First [Member] | System Conversion Costs [Member]
Business Combination, Acquisition Related Costs				481,000
Community First [Member] | Contract Termination Fees [Member]
Business Combination, Acquisition Related Costs				427,000
Community First [Member] | Legal Fees [Member]
Business Combination, Acquisition Related Costs				330,000
Community First [Member] | Accounting and Auditing Fees [Member]
Business Combination, Acquisition Related Costs				50,000
Community First [Member] | Other Costs [Member]
Business Combination, Acquisition Related Costs				228,000
Community First [Member] | Core Deposits [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	$ 1,200,000
Finite-Lived Intangible Asset, Useful Life	10 years
Amortization of Intangible Assets, Total	$ 30,000
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	121,000
Finite-Lived Intangible Assets, Amortization Expense, Year Two	121,000
Finite-Lived Intangible Assets, Amortization Expense, Year Three	121,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four	121,000
Finite-Lived Intangible Assets, Amortization Expense, Year Five	121,000
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	$ 574,000
Community First [Member] | Common Stock [Member]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares	419,173
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned	$ 15,600,000
Business Combination, Step Acquisition, Equity Interest in Acquiree, Shares	18,000
Business Combination, Step Acquisition, Equity Interest in Acquiree, Gain on Retirement	$ 690,000
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable	15,636,000
Community First [Member] | Preferred Stock [Member]
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned	$ 4,200,000
Business Acquisition, Number of Shares Received	420,593
Business Acquisition, Number of Shares Received, Value	$ 4,200,000
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable	$ 4,206,000
Northern Hancock Bank & Trust Co. [Member]
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares		54,445
Payments to Acquire Businesses, Gross		$ 22,000	$ 22,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles		167,000	167,000
Business Combination, Acquired Receivable, Fair Value							$ 18,500,000
Business Combination, Loans Receivable, Credit Adjustment		566,000
Business Combination, Loans Receivable, Other Adjustment		537,000
Business Combination, Acquisition Related Costs					1,100,000
Business Combination, Consideration Transferred, Equity Interests Issued and Issuable		1,700,000	1,674,000
Business Combination, Bargain Purchase, Gain Recognized, Amount		1,300,000	1,316,000
Northern Hancock Bank & Trust Co. [Member] | Employee Non-Compete and Severance Costs [Member]
Business Combination, Acquisition Related Costs					108,000
Northern Hancock Bank & Trust Co. [Member] | System Conversion Costs [Member]
Business Combination, Acquisition Related Costs					421,000
Northern Hancock Bank & Trust Co. [Member] | Contract Termination Fees [Member]
Business Combination, Acquisition Related Costs					279,000
Northern Hancock Bank & Trust Co. [Member] | Legal Fees [Member]
Business Combination, Acquisition Related Costs					173,000
Northern Hancock Bank & Trust Co. [Member] | Accounting and Auditing Fees [Member]
Business Combination, Acquisition Related Costs					55,000
Northern Hancock Bank & Trust Co. [Member] | Other Costs [Member]
Business Combination, Acquisition Related Costs					$ 84,000
Northern Hancock Bank & Trust Co. [Member] | Core Deposits [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles		167,000	167,000
Amortization of Intangible Assets, Total				$ 40,000
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months		30,000	30,000
Finite-Lived Intangible Assets, Amortization Expense, Year Two		22,000	22,000
Finite-Lived Intangible Assets, Amortization Expense, Year Three		17,000	17,000
Finite-Lived Intangible Assets, Amortization Expense, Year Four		13,000	13,000
Finite-Lived Intangible Assets, Amortization Expense, Year Five		13,000	13,000
Finite-Lived Intangible Assets, Amortization Expense, after Year Five		$ 21,000	$ 21,000
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life		8 years