Parent Company Only Condensed Financial Information - Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net income	$ 13,356	$ 15,446	$ 15,951	$ 15,844	$ 5,702	$ 16,011	$ 15,575	$ 14,556	$ 60,597	$ 51,844	$ 41,876
NET CASH FROM OPERATING ACTIVITIES									83,685	54,933	49,066
Cash flows from investing activities:
NET CASH FROM INVESTING ACTIVITIES									(208,453)	(423,613)	(159,887)
Cash flows from financing activities:
Proceeds from long term borrowings									0	73,749	0
Repurchase of common shares									0	(164)	(14,238)
Cash dividends paid									(22,004)	(14,072)	(12,654)
NET CASH FROM FINANCING ACTIVITIES									87,529	226,849	294,682
NET CHANGE IN CASH AND CASH EQUIVALENTS									(37,239)	(141,831)	183,861
Farmers National Banc Corp
Cash flows from operating activities:
Net income									60,597	51,844	41,876
Dividends in excess of net income (Equity in undistributed net income of subsidiaries)									(26,731)	(5,247)	(12,461)
Other									559	6,846	1,167
NET CASH FROM OPERATING ACTIVITIES									34,425	53,443	30,582
Cash flows from investing activities:
Net cash paid in business combinations									0	(29,618)	(20,423)
NET CASH FROM INVESTING ACTIVITIES									0	(29,618)	(20,423)
Cash flows from financing activities:
Proceeds from long term borrowings									0	73,749	0
Repurchase of common shares									0	(164)	(14,238)
Cash dividends paid									(22,004)	(14,072)	(12,654)
NET CASH FROM FINANCING ACTIVITIES									(22,004)	59,513	(26,892)
NET CHANGE IN CASH AND CASH EQUIVALENTS									12,421	83,338	(16,733)
Beginning cash and cash equivalents				$ 92,076				$ 8,738	92,076	8,738	25,471
Ending cash and cash equivalents	$ 104,497				$ 92,076				$ 104,497	$ 92,076	$ 8,738