Parent Company Only Condensed Financial Information - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Assets:
Equity securities	$ 6,881	$ 7,909
Other	46,821	36,615
TOTAL ASSETS	3,071,148	2,449,158
Liabilities:
Other liabilities	31,267	18,688
TOTAL LIABILITIES	2,721,051	2,149,849
TOTAL STOCKHOLDERS' EQUITY	350,097	299,309	$ 262,320
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	3,071,148	2,449,158
Farmers National Banc Corp
Assets:
Cash	8,738	25,471
Equity securities	358	432
Other	0	1,273
TOTAL ASSETS	361,001	302,096
Liabilities:
Other liabilities	1,149	131
Note payable	350	350
Subordinate debt	9,405	2,306
TOTAL LIABILITIES	10,904	2,787
TOTAL STOCKHOLDERS' EQUITY	350,097	299,309
TOTAL LIABILITIES AND STOCKHOLDERS' EQUITY	361,001	302,096
Farmers National Banc Corp | Bank Segment
Assets:
Investment in subsidiaries	336,326	259,628
Farmers National Banc Corp | Farmers Trust
Assets:
Investment in subsidiaries	13,414	13,106
Farmers National Banc Corp | Captive Insurance
Assets:
Investment in subsidiaries	$ 2,165	$ 2,186