XML 139 R123.htm IDEA: XBRL DOCUMENT v3.20.4

SUBSEQUENT EVENTS (Details) $ in Millions	Jan. 20, 2021 USD ($)
Community Capital Trust IV | Subsequent event
Subsequent Event [Line Items]
Authorized amount of debentures and associated preferred securities for redemption	$ 77.3

X

- Definition

Board of directors approved amount for redemption of debentures and associated preferred securities.

+ References

No definition available.

+ Details

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

X

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

X

- Details

Name:	srt_OwnershipAxis=cbu_CommunityStatutoryTrust4Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: