XML 65 R53.htm IDEA: XBRL DOCUMENT v3.25.3

FAIR VALUE - Assets and liabilities measured on a non-recurring basis (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024	Feb. 01, 2024
Assets and Liabilities Measured on Nonrecurring Basis
Impairment recovery				$ 100
Acquisition-related contingent consideration adjustment			$ 156		$ 156
Payments of contingent consideration for acquisitions				(932)	$ (2,690)
Payment for contingent consideration, investing	$ 500
CPD
Assets and Liabilities Measured on Nonrecurring Basis
Payment for contingent consideration, investing		$ 100
Revenue-based contingent consideration		$ 600					$ 2,000
Mortgage servicing rights
Assets and Liabilities Measured on Nonrecurring Basis
Valuation allowance	0			0		$ 100
Non-recurring
Assets and Liabilities Measured on Nonrecurring Basis
Individually assessed loans	14,334			14,334		19,315
Other real estate owned	5,635			5,635		2,781
Mortgage servicing rights	1,263			1,263		460
Contingent consideration	(6,814)			(6,814)		(4,140)
Total	14,418			14,418		18,416
Non-recurring | Level 1
Assets and Liabilities Measured on Nonrecurring Basis
Individually assessed loans	0			0		0
Other real estate owned	0			0		0
Mortgage servicing rights	0			0		0
Contingent consideration	0			0		0
Total	0			0		0
Non-recurring | Level 2
Assets and Liabilities Measured on Nonrecurring Basis
Individually assessed loans	0			0		0
Other real estate owned	0			0		0
Mortgage servicing rights	0			0		0
Contingent consideration	0			0		0
Total	0			0		0
Non-recurring | Level 3
Assets and Liabilities Measured on Nonrecurring Basis
Individually assessed loans	14,334			14,334		19,315
Other real estate owned	5,635			5,635		2,781
Mortgage servicing rights	1,263			1,263		460
Contingent consideration	(6,814)			(6,814)		(4,140)
Total	$ 14,418			$ 14,418		$ 18,416

X

- Definition

Represents the fair value of contingent consideration.

+ References

No definition available.

+ Details

Name:	cbu_ContingentConsiderationFairValueDisclosure
Namespace Prefix:	cbu_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of allowance for credit losses related to specifically allocated.

+ References

No definition available.

+ Details

Name:	cbu_ImpairedFinancingReceivableSpecificallyAllocatedAllowance
Namespace Prefix:	cbu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- Definition

This is the amount of impaired loans carried at fair value.

+ References

No definition available.

+ Details

Name:	cbu_ImpairedLoansFairValueDisclosure
Namespace Prefix:	cbu_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of increase (decrease) in value of liability in contingent consideration arrangement in business combination, including, but not limited to, difference arising upon settlement.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479581/805-30-50-4

+ Details

Name:	us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Maximum amount of estimate for undiscounted range of outcomes in contingent consideration arrangement in business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479328/805-10-50-8

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 805
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 43
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479303/805-10-55-43

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479581/805-30-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479581/805-30-50-1

+ Details

Name:	us-gaap_BusinessCombinationContingentConsiderationArrangementsRangeOfOutcomesValueHigh
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

X

- References

No definition available.

+ Details

Name:	us-gaap_FairValueMeasurementsNonrecurringValueMeasurementAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Fair value of asset after deduction of liability.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

+ Details

Name:	us-gaap_FairValueNetAssetLiability
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

The adjustment to the carrying value of the rights retained or purchased to service mortgages. These adjustments are made when the estimate of the fair value is changed. This element is a noncash adjustment to net income when calculating net cash generated by operating activities using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)(6)
-SubTopic 50
-Topic 860
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481229/860-50-50-4

+ Details

Name:	us-gaap_MortgageServicingRightsMSRImpairmentRecovery
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Carrying amount of other real estate not separately disclosed, including, but not limited to, real estate investments, real estate loans that qualify as investments in real estate, and premises that are no longer used in operations may also be included in real estate owned. This does not include real estate assets taken in settlement of troubled loans through surrender or foreclosure.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10)(4))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

+ Details

Name:	us-gaap_OtherRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Amount of cash outflow, not made soon after acquisition date of business combination, to settle contingent consideration liability up to amount recognized at acquisition date, including, but not limited to, measurement period adjustment and less amount paid soon after acquisition date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 15
-Subparagraph (f)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-15

+ Details

Name:	us-gaap_PaymentForContingentConsiderationLiabilityFinancingActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Amount of cash outflow, made soon after acquisition date of business combination, to settle contingent consideration liability.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 13
-Subparagraph (d)
-SubTopic 10
-Topic 230
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-13

+ Details

Name:	us-gaap_PaymentForContingentConsiderationLiabilityInvestingActivities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

Fair value of contract to service financial assets under which the benefits of servicing are expected to more than adequately compensate the servicer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 50
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481229/860-50-50-4

+ Details

Name:	us-gaap_ServicingAssetAtAmortizedValueFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	us-gaap_BusinessAcquisitionAxis=cbu_CertainAssetsOfCreativePlanDesignLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByAssetClassAxis=cbu_MortgageServicingRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsNonrecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: