v2.4.0.8

LOANS, Credit Quality By Past Due Status (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014		Dec. 31, 2013
Aged analysis of the company's loans [Abstract]
Total Loans	$ 4,096,358		$ 4,109,083
Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Past Due 30 - 89 Days	24,469		35,689
90 + Days Past Due and Still Accruing	1,826		2,418
Nonaccrual	17,755		16,065
Total Past Due	44,050		54,172
Current	3,730,056		3,717,703
Total Loans	3,774,106		3,771,875
Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Past Due 30 - 89 Days	3,121		3,522
90 + Days Past Due and Still Accruing	151		137
Nonaccrual	3,914		3,408
Total Past Due	7,186		7,067
Acquired Impaired	6,143	[1]	7,090	[1]
Current	308,923		323,051
Total Loans	322,252		337,208
Consumer Mortgage [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Past Due 30 - 89 Days	8,924		16,589
90 + Days Past Due and Still Accruing	953		1,253
Nonaccrual	12,605		11,097
Total Past Due	22,482		28,939
Current	1,479,605		1,473,320
Total Loans	1,502,087		1,502,259
Consumer Mortgage [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Past Due 30 - 89 Days	891		1,857
90 + Days Past Due and Still Accruing	143		85
Nonaccrual	1,828		1,463
Total Past Due	2,862		3,405
Acquired Impaired	0	[1]	0	[1]
Current	74,373		76,394
Total Loans	77,235		79,799
Business Lending [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Past Due 30 - 89 Days	5,440		2,960
90 + Days Past Due and Still Accruing	54		164
Nonaccrual	3,119		3,083
Total Past Due	8,613		6,207
Current	1,070,832		1,079,818
Total Loans	1,079,445		1,086,025
Business Lending [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Past Due 30 - 89 Days	1,278		531
90 + Days Past Due and Still Accruing	0		0
Nonaccrual	1,618		1,472
Total Past Due	2,896		2,003
Acquired Impaired	6,143	[1]	7,090	[1]
Current	157,586		165,246
Total Loans	166,625		174,339
Consumer Indirect [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Past Due 30 - 89 Days	7,550		11,647
90 + Days Past Due and Still Accruing	680		738
Nonaccrual	13		14
Total Past Due	8,243		12,399
Current	744,818		723,878
Total Loans	753,061		736,277
Consumer Indirect [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Past Due 30 - 89 Days	130		157
90 + Days Past Due and Still Accruing	2		17
Nonaccrual	0		0
Total Past Due	132		174
Acquired Impaired	0	[1]	0	[1]
Current	2,656		3,551
Total Loans	2,788		3,725
Consumer Direct [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Past Due 30 - 89 Days	1,196		1,858
90 + Days Past Due and Still Accruing	53		90
Nonaccrual	3		4
Total Past Due	1,252		1,952
Current	165,332		169,452
Total Loans	166,584		171,404
Consumer Direct [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Past Due 30 - 89 Days	283		385
90 + Days Past Due and Still Accruing	6		27
Nonaccrual	0		0
Total Past Due	289		412
Acquired Impaired	0	[1]	0	[1]
Current	7,484		8,323
Total Loans	7,773		8,735
Home Equity [Member] | Legacy Loan [Member]
Aged analysis of the company's loans [Abstract]
Past Due 30 - 89 Days	1,359		2,635
90 + Days Past Due and Still Accruing	86		173
Nonaccrual	2,015		1,867
Total Past Due	3,460		4,675
Current	269,469		271,235
Total Loans	272,929		275,910
Home Equity [Member] | Acquired Loans [Member]
Aged analysis of the company's loans [Abstract]
Past Due 30 - 89 Days	539		592
90 + Days Past Due and Still Accruing	0		8
Nonaccrual	468		473
Total Past Due	1,007		1,073
Acquired Impaired	0	[1]	0	[1]
Current	66,824		69,537
Total Loans	$ 67,831		$ 70,610
[1] Acquired impaired loans were not classified as nonperforming assets as the loans are considered to be performingunder ASC 310-30. As a result interest income, through the accretion of the difference between the carryingamount of the loans and the expected cashflows, is being recognized on acquired impaired loans.

X

- Definition

Financing receivables that are less than 90 days past due but more than 29 days past due.

+ References

No definition available.

+ Details

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

X

- Definition

Loans acquired after January 1, 2009 that have evidence of deterioration in credit quality since origination and for which it is probable, at acquisition, that the company will be unable to collect all contractually required payments.

+ References

No definition available.

+ Details

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

X

- Definition

Recorded investment in financing receivables that are 90 days or more past due and still accruing.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5111-111524

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X

- Definition

Financing receivables that are current.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7A

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953401-111524

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Balance Type:	debit
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X

- Definition

Recorded investment in financing receivables that are on nonaccrual status as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7

-Subparagraph (d)

-URI http://asc.fasb.org/extlink&oid=28368275&loc=d3e5111-111524

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Balance Type:	debit
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X

- Definition

Recorded Investment in financing receivables that are past due at the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 7A

-URI http://asc.fasb.org/extlink&oid=28368275&loc=SL6953401-111524

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X

- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=28367877&loc=d3e4428-111522

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