Parent Company Only Condensed Financial Information - Statements of Income (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
Income:
Dividends from subsidiaries									$ 871	$ 498	$ 543
Income tax benefit	$ (2,765)	$ (3,315)	$ (3,160)	$ (2,998)	$ (508)	$ (3,358)	$ (3,303)	$ (3,101)	(12,238)	(10,270)	(8,396)
NET INCOME	$ 13,356	$ 15,446	$ 15,951	$ 15,844	$ 5,702	$ 16,011	$ 15,575	$ 14,556	60,597	51,844	41,876
Farmers National Banc Corp
Income:
Interest and dividends on securities									0	11	12
Security gains/(losses)									0	130	(28)
Total Income									39,400	49,696	31,930
Interest on borrowings									(3,428)	(918)	(361)
Other expenses									(3,451)	(2,792)	(2,746)
Income before income tax benefit and undistributed subsidiary income									32,521	45,986	28,823
Income tax benefit									1,345	611	592
Equity in undistributed net income of subsidiaries (dividends in excess of net income)									26,731	5,247	12,461
NET INCOME									60,597	51,844	41,876
Farmers National Banc Corp | Bank Segment
Income:
Dividends from subsidiaries									30,000	45,620	28,646
Equity in undistributed net income of subsidiaries (dividends in excess of net income)									25,935	4,412	12,244
Farmers National Banc Corp | Farmers Trust
Income:
Dividends from subsidiaries									8,000	2,800	2,300
Equity in undistributed net income of subsidiaries (dividends in excess of net income)									662	412	237
Farmers National Banc Corp | Captive Insurance
Income:
Dividends from subsidiaries									1,400	1,135	1,000
Equity in undistributed net income of subsidiaries (dividends in excess of net income)									$ 134	$ 423	$ (20)