Parent Company (Franklin Financial Services Corporation) Financial Information (Schedule Of Condensed Cash Flow Statement) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Net income	$ 1,723	$ 2,075	$ 1,561	$ 2,726	$ 2,267	$ 2,579	$ 2,474	$ 2,884	$ 8,087	$ 10,204	$ 8,402
Adjustments to reconcile net income to net cash provided by operating activities:
Stock option compensation									88	74
Securities gains, net	8	$ (10)	$ 2	(28)			$ 8	718	22	8	280
Net cash provided by operating activities									14,856	13,290	14,356
Proceeds from sales of investment securities									3,825	1,381	5,421
Net cash used in investing activities									(102,670)	(49,168)	(12,942)
Dividends paid									(3,523)	(3,139)	(2,847)
Common stock issued under stock option plans									82	92	59
Common stock issued under dividend reinvestment plan									1,671	1,246	923
Treasury stock purchase									(795)
Net cash provided by financing activities									85,313	26,451	6,434
Increase (decrease) in cash and cash equivalents									(2,501)	(9,427)	7,848
Cash and cash equivalents as of January 1				39,166				48,593	39,166	48,593	40,745
Cash and cash equivalents as of December 31	36,665				39,166				36,665	39,166	48,593
Franklin Financial Service Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Net income									8,087	10,204	8,402
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed income of subsidiary									(4,752)	(10,391)	(7,708)
Stock option compensation									88	74
Securities gains, net											82
(Increase) decrease in other assets/liabilities									(307)	1,800	498
Net cash provided by operating activities									3,116	1,687	1,110
Proceeds from sales of investment securities											568
Net cash used in investing activities											568
Dividends paid									(3,523)	(3,139)	(2,847)
Common stock issued under stock option plans									82	92	59
Common stock issued under dividend reinvestment plan									1,671	1,246	923
Treasury stock purchase									(795)
Net cash provided by financing activities									(2,565)	(1,801)	(1,865)
Increase (decrease) in cash and cash equivalents									551	(114)	(187)
Cash and cash equivalents as of January 1				$ 300				$ 414	300	414	601
Cash and cash equivalents as of December 31	$ 851				$ 300				$ 851	$ 300	$ 414