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Equity Compensation (Details Textual) - USD ($)	3 Months Ended		9 Months Ended
Equity Compensation (Details Textual) - USD ($)	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Omnibus Equity Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized	340,000		340,000
Equity compensation expense recorded	$ 126,000	$ 58,000	$ 627,000	$ 144,000
Unrecognized compensation expense	365,000		$ 365,000
Unrecognized compensation expense, expected to be recognized			8 months 27 days
Shares awarded under the plan, vesting description			Shares awarded under this plan can vest immediately and/or on the anniversary of the award date from one to three years out if the employee remains employed with Cortland Bancorp.
Omnibus Equity Plan \| Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares granted under the plan			30,156	12,593
Director Equity Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Equity compensation expense recorded	$ 0	$ 0	$ 34,000	$ 22,000
Director Equity Plan \| Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized	113,000		113,000
Shares granted under the plan			1,525	989
Minimum \| Omnibus Equity Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period			1 year
Maximum \| Omnibus Equity Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period			3 years