Parent Company (Franklin Financial Services Corporation) Condensed Financial Information (Statements Of Income) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Condensed Financial Statements, Captions [Line Items]
Change in fair value of equity securities	$ 16	$ (69)
Interest expense	23,125	4,863
Income before federal income taxes	15,753	17,495
Income tax benefit	(2,155)	(2,557)
Net income	13,598	14,938
Total other comprehensive gain (loss)	10,347	(50,740)
Total Comprehensive Income (Loss)	23,945	(35,802)
Franklin Financial Services Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Dividends from Bank subsidiary	5,607	5,670
Change in fair value of equity securities	16	(69)
Dividends	7	5
Income	5,630	5,606
Interest expense	1,051	1,047
Operating expenses	1,887	1,771
Income before federal income taxes	2,692	2,788
Income tax benefit	894	600
Equity in undistributed income of subsidiaries	10,012	11,550
Net income	13,598	14,938
Total other comprehensive gain (loss)	10,347	(50,740)
Total Comprehensive Income (Loss)	$ 23,945	$ (35,802)