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- References

No definition available.

Name:	cbu_TimeDepositsMaturities250000OrMoreAbstract
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he amount maturities of domestic and foreign time deposits (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $250,000 or more, after five years from the balance sheet date.

No definition available.

Name:	cbu_TimeDepositsMaturities250000OrMoreAfterYearFive
Namespace Prefix:	cbu_
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The amount of maturities domestic and foreign time deposits (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $250,000 or more, for next twelve months from the balance sheet date.

No definition available.

Name:	cbu_TimeDepositsMaturities250000OrMoreNextTwelveMonths
Namespace Prefix:	cbu_
Data Type:	xbrli:monetaryItemType
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The amount maturities of domestic and foreign time deposits (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $250,000 or more, for year five from the balance sheet date.

No definition available.

Name:	cbu_TimeDepositsMaturities250000OrMoreYearFive
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No definition available.

Name:	cbu_TimeDepositsMaturities250000OrMoreYearFour
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The amount of maturities of domestic and foreign time deposits (including certificates of deposits, individual retirement accounts and open accounts) in denominations of $250,000 or more, for year three from the balance sheet date.

No definition available.

Name:	cbu_TimeDepositsMaturities250000OrMoreYearThree
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Data Type:	xbrli:monetaryItemType
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No definition available.

Name:	cbu_TimeDepositsMaturities250000OrMoreYearTwo
Namespace Prefix:	cbu_
Data Type:	xbrli:monetaryItemType
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The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.12)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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- References

No definition available.

Name:	us-gaap_DepositsAbstract
Namespace Prefix:	us-gaap_
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Amount of deposits in accounts that offer many of the same services as checking accounts although transactions may be somewhat more limited, share some of the characteristics of a money market fund and are insured by the Federal government, also known as money market accounts.

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Amount of interest bearing deposits with no stated maturity, which may include passbook and statement savings accounts and money-market deposit accounts (MMDAs).

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount of interest-bearing domestic checking deposit liabilities.

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Period Type:	instant

Amount of noninterest-bearing domestic checking deposit liabilities.

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Amount of time deposits maturing after the fifth fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of time deposits maturing in the fifth fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of time deposits maturing in the fourth fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of time deposits maturing in the next fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6802200&loc=d3e1835-112601

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Industry Guide
-Number 3
-Section V
-Paragraph D-E

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Amount of time deposits maturing in the third fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of time deposits maturing in the second fiscal year following the latest fiscal year. Time deposits include, but are not limited to, certificates of deposits. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Amount of time deposit liabilities, including certificates of deposit.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 405
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=50488274&loc=d3e64164-112818

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.12)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Industry Guide
-Number 3
-Section V
-Paragraph D-E

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- References

No definition available.