Capital Ratios (Schedule Of The Total Risk-based, Tier 1 Risk-based And Tier 1 Leverage Requirements) (Details)	Mar. 31, 2026	Dec. 31, 2025
Franklin Financial Services Corporation [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 Risk-based Capital Ratio: Ratio	0.1181	0.1145
Tier 1 Risk-based Capital Ratio: Ratio	0.1181	0.1145
Total Risk-based Capital Ratio: Ratio	0.1366	0.1327
Tier 1 Leverage Ratio: Ratio	0.0857	0.0817
Farmers & Merchants Trust Company [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Common Equity Tier 1 Risk-based Capital Ratio: Ratio	0.1239	0.1202
Common Equity Tier 1 Risk-based Capital Ratio: Adequately Capitalized Minimum: Ratio	0.0450
Common Equity Tier 1 Risk-based Capital Ratio: Well Capitalized Minimum: Ratio	0.0650
Tier 1 Risk-based Capital Ratio: Ratio	0.1239	0.1202
Tier 1 Risk-based Capital Ratio: Adequately Capitalized Minimum: Ratio	0.0600
Tier 1 Risk-based Capital Ratio: Well Capitalized Minimum: Ratio	0.0800
Total Risk-based Capital Ratio: Ratio	0.1364	0.1327
Total Risk-based Capital Ratio: Adequately Capitalized Minimum: Ratio	0.0800
Total Risk-based Capital Ratio: Well Capitalized Minimum: Ratio	0.1000
Tier 1 Leverage Ratio: Ratio	0.0899	0.0857
Tier 1 Leverage Ratio: Adequately Capitalized Minimum: Ratio	0.0400
Tier 1 Leverage Ratio: Well Capitalized Minimum: Ratio	0.0500

Tangible Capital Required For Well Capitalized To Tangible Assets

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Ratio of minimum total risk-based capital to risk-weighted assets required for capital adequacy as defined by regulatory framework.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 505
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Ratio of minimum total risk-based capital to risk-weighted assets categorized as well capitalized as defined by regulatory framework for prompt corrective action.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Ratio of minimum tangible capital to tangible assets required for capital adequacy as defined by regulatory framework.

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