Note 11 - Regulatory Matters - Regulatory Ratios of the Consolidated Company and Its Subsidiary Banks (Details)		Sep. 30, 2016	Dec. 31, 2015
Consolidated Entities [Member]
Common Equity Tier 1 Risk-based Capital	[1]	16.65%	14.91%
Tier 1 Risk-based Capital	[1]	19.57%	19.00%
Total Risk-based Capital	[1]	20.39%	19.89%
Tier 1 Leverage	[2]	12.44%	12.46%
Farmers Bank [Member]
Common Equity Tier 1 Risk-based Capital	[1]	17.12%	15.57%
Tier 1 Risk-based Capital	[1]	17.12%	15.57%
Total Risk-based Capital	[1]	17.84%	16.35%
Tier 1 Leverage	[2]	9.53%	9.20%
United Bank [Member]
Common Equity Tier 1 Risk-based Capital	[1]	17.54%	18.67%
Tier 1 Risk-based Capital	[1]	17.54%	18.67%
Total Risk-based Capital	[1]	18.51%	19.68%
Tier 1 Leverage	[2]	12.46%	12.89%
First Citizens Bank [Member]
Common Equity Tier 1 Risk-based Capital	[1]	14.73%	13.55%
Tier 1 Risk-based Capital	[1]	14.73%	13.55%
Total Risk-based Capital	[1]	15.32%	14.17%
Tier 1 Leverage	[2]	10.08%	9.20%
Citizens Northern [Member]
Common Equity Tier 1 Risk-based Capital	[1]	15.37%	14.42%
Tier 1 Risk-based Capital	[1]	15.37%	14.42%
Total Risk-based Capital	[1]	16.43%	15.67%
Tier 1 Leverage	[2]	10.43%	10.79%
Common Equity Tier 1 Risk-based Capital, Regulatory minimum	[1]	4.50%	4.50%
Tier 1 Risk-based Capital, Regulatory minimum	[1]	6.00%	6.00%
Total Risk-based Capital, Regulatory minimum	[1]	8.00%	8.00%
Tier 1 Leverage, Regulatory minimum	[2]	4.00%	4.00%
Common Equity Tier 1 Risk-based Capital, Well-capitalized status	[1]	6.50%	6.50%
Tier 1 Risk-based Capital, Well-capitalized status	[1]	8.00%	8.00%
Total Risk-based Capital, Well-capitalized status	[1]	10.00%	10.00%
Tier 1 Leverage, Well-capitalized status	[2]	5.00%	5.00%

[1] Common Equity Tier 1 Risked-based, Tier 1 Risk-based, and Total Risk-based Capital ratios are computed by dividing a bank's Common Equity Tier 1, Tier 1 or Total Capital, as defined by regulation, by a risk-weighted sum of the bank's assets, with the risk weighting determined by general standards established by regulation.

[2] Tier 1 Leverage ratio is computed by dividing a bank's Tier 1 Capital by its total quarterly average assets, as defined by regulation.