Significant Accounting Policies - Valuation of Investments (Details) - Community Financial System, Inc. 401(k) Employee Stock Ownership Plan - USD ($) |
12 Months Ended | |
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Dec. 31, 2025 |
Dec. 31, 2024 |
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| Significant Accounting Policies | ||
| Processing period | 1 day | |
| Unfunded commitments | $ 0 | |
| Stable Value Fund | ||
| Significant Accounting Policies | ||
| Percentage of total return | 6.45% | 3.17% |
| Percentage of crediting interest | 3.06% | 2.77% |
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- Definition Percentage of crediting interest rate on investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). No definition available.
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- Definition Percentage of total return on investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). No definition available.
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- Definition Processing period for participant-directed withdrawals in employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). No definition available.
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- Definition Amount of unfunded commitment for investment held by employee stock purchase, saving, or similar plan (employee benefit plan (EBP)), that is fair value measured at net asset value (NAV) per share as practical expedient. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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- Definition 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. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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