XML 53 R42.htm IDEA: XBRL DOCUMENT
v3.23.3

INVESTMENT SECURITIES - Investment Securities Pledged as Collateral (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended |
--- | --- | --- | ---
Sep. 30, 2023 | Sep. 30, 2022 | Sep. 30, 2023 | Sep. 30, 2022 | Dec. 31, 2022
Investment Securities Pledged as Collateral |  |  |  |  |
Investment securities pledged to collateralize certain deposits and borrowings | $ 2,190,000 |  | $ 2,190,000 |  | $ 2,180,000
Gross realized losses | 0 | $ 0 | (52,329) | $ 0 |
Proceeds from sales of available-for-sale investment securities |  |  | 733,789 | $ 0 |
U.S. Treasury and agency securities |  |  |  |  |
Investment Securities Pledged as Collateral |  |  |  |  |
Book value of available-for-sale | 786,100 |  | 786,100 |  |
Gross realized losses |  |  | 52,300 |  |
Proceeds from sales of available-for-sale investment securities |  |  | 733,800 |  |
U.S. Treasury and agency securities | Securities Sold under Agreements to Repurchase |  |  |  |  |
Investment Securities Pledged as Collateral |  |  |  |  |
Investment securities pledged to collateralize certain deposits and borrowings | $ 542,800 |  | $ 542,800 |  | $ 466,900

X
- Definition Book value of investment in debt securities, available-for-sale, sold by the entity. + References No definition available. + Details
Name: | cbu_DebtSecuritiesAvailableForSaleBookValueOfSecuritiesSold
Namespace Prefix: | cbu_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, after allowance for credit loss, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), investment in debt security measured at amortized cost (held-to-maturity), and investment in debt security measured at fair value with change in fair value recognized in net income (trading). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(1)(a)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481830/320-10-45-1 + Details
Name: | us-gaap_DebtSecurities
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-9 + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleRealizedGainLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_FinancialInstrumentsOwnedAndPledgedAsCollateralAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 11 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481830/320-10-45-11 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 320 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 9 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147481800/320-10-50-9 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482740/230-10-45-12 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 230 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 11 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482740/230-10-45-11 + Details
Name: | us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ShortTermDebtTypeAxis=us-gaap_SecuritiesSoldUnderAgreementsToRepurchaseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |