PARENT COMPANY ONLY - Condensed Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
ASSETS
Other assets	$ 46,681	$ 39,819
TOTAL ASSETS	2,515,584	2,454,307
LIABILITIES AND STOCKHOLDERS' EQUITY
Senior notes, net	14,831	14,765
Subordinated debt, net	24,717	24,607
Accrued interest and other liabilities	26,638	25,608
Stockholders' equity	262,381	249,325	$ 301,405	$ 299,756
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	2,515,584	2,454,307
Parent Company
ASSETS
Cash	14,822	17,867
Other assets	200	33
TOTAL ASSETS	302,128	288,799
LIABILITIES AND STOCKHOLDERS' EQUITY
Senior notes, net	14,831	14,765
Subordinated debt, net	24,717	24,607
Accrued interest and other liabilities	199	102
Stockholders' equity	262,381	249,325
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	302,128	288,799
Subsidiaries [Member] | Citizens and Northern Bank [Member]
ASSETS
Investment in subsidiaries	272,286	254,809
Subsidiaries [Member] | Citizens and Northern Investment Corporation [Member]
ASSETS
Investment in subsidiaries	11,087	12,453
Subsidiaries [Member] | Bucktail Life Insurance Company [Member]
ASSETS
Investment in subsidiaries	$ 3,733	$ 3,637