XML 55 R44.htm IDEA: XBRL DOCUMENT
v3.23.2

LOANS AND ALLOWANCE FOR CREDIT LOSSES - Amount of Business Lending Loans by Credit Quality Categories (Details) - USD ($) $ in Thousands | 3 Months Ended | 6 Months Ended |
--- | --- | --- | ---
Jun. 30, 2023 | Jun. 30, 2022 | Jun. 30, 2023 | Jun. 30, 2022 | Dec. 31, 2022
Term loans amortized cost basis by origination year |  |  |  |  |
Total Loans | $ 9,170,769 |  | $ 9,170,769 |  | $ 8,809,394
Total Loans | 2,758 | $ 2,147 | 5,988 | $ 4,303 |
Legacy Loan |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Total Loans | 9,170,769 |  | 9,170,769 |  | 8,809,394
Business lending |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 211,224 |  | 211,224 |  | 752,160
Year Two | 680,020 |  | 680,020 |  | 379,524
Year Three | 358,168 |  | 358,168 |  | 237,510
Year Four | 221,960 |  | 221,960 |  | 253,692
Year Five | 237,871 |  | 237,871 |  | 195,296
Prior | 816,086 |  | 816,086 |  | 688,510
Revolving Loans Amortized Cost Basis | 750,513 |  | 750,513 |  | 686,761
Revolving Loans Converted to Term | 557,855 |  | 557,855 |  | 452,212
Total Loans | 3,833,697 |  | 3,833,697 |  | 3,645,665
Year One |  |  | 0 |  |
Year Two |  |  | 91 |  |
Year Three |  |  | 0 |  |
Year Four |  |  | 0 |  |
Year Five |  |  | 0 |  |
Prior |  |  | 0 |  |
Revolving Loans Amortized Cost Basis |  |  | 388 |  |
Revolving Loans Converted to Term |  |  | 0 |  |
Total Loans |  |  | 479 |  |
Business lending | Pass |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 209,211 |  | 209,211 |  | 747,573
Year Two | 674,608 |  | 674,608 |  | 373,913
Year Three | 352,847 |  | 352,847 |  | 232,591
Year Four | 214,130 |  | 214,130 |  | 246,820
Year Five | 230,351 |  | 230,351 |  | 168,468
Prior | 733,925 |  | 733,925 |  | 604,745
Revolving Loans Amortized Cost Basis | 712,466 |  | 712,466 |  | 646,771
Revolving Loans Converted to Term | 504,510 |  | 504,510 |  | 401,531
Total Loans | 3,632,048 |  | 3,632,048 |  | 3,422,412
Business lending | Special Mention |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 1,546 |  | 1,546 |  | 2,787
Year Two | 2,533 |  | 2,533 |  | 4,836
Year Three | 4,693 |  | 4,693 |  | 3,781
Year Four | 5,554 |  | 5,554 |  | 3,676
Year Five | 4,564 |  | 4,564 |  | 14,593
Prior | 53,689 |  | 53,689 |  | 45,627
Revolving Loans Amortized Cost Basis | 26,057 |  | 26,057 |  | 29,403
Revolving Loans Converted to Term | 34,197 |  | 34,197 |  | 29,975
Total Loans | 132,833 |  | 132,833 |  | 134,678
Business lending | Classified |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 467 |  | 467 |  | 1,800
Year Two | 2,879 |  | 2,879 |  | 775
Year Three | 628 |  | 628 |  | 1,138
Year Four | 2,276 |  | 2,276 |  | 3,196
Year Five | 2,956 |  | 2,956 |  | 12,235
Prior | 28,472 |  | 28,472 |  | 38,138
Revolving Loans Amortized Cost Basis | 11,990 |  | 11,990 |  | 10,587
Revolving Loans Converted to Term | 19,148 |  | 19,148 |  | 20,706
Total Loans | 68,816 |  | 68,816 |  | 88,575
Business lending | Doubtful |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 0 |  | 0 |  | 0
Year Two | 0 |  | 0 |  | 0
Year Three | 0 |  | 0 |  | 0
Year Four | 0 |  | 0 |  | 0
Year Five | 0 |  | 0 |  | 0
Prior | 0 |  | 0 |  | 0
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total Loans | 0 |  | 0 |  | 0
Consumer mortgage |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 183,523 |  | 183,523 |  | 539,679
Year Two | 523,401 |  | 523,401 |  | 672,042
Year Three | 650,837 |  | 650,837 |  | 332,352
Year Four | 318,772 |  | 318,772 |  | 255,089
Year Five | 242,981 |  | 242,981 |  | 157,548
Prior | 1,026,750 |  | 1,026,750 |  | 944,971
Revolving Loans Amortized Cost Basis | 26,311 |  | 26,311 |  | 28,989
Revolving Loans Converted to Term | 99,515 |  | 99,515 |  | 81,805
Total Loans | 3,072,090 |  | 3,072,090 |  | 3,012,475
Year One |  |  | 0 |  |
Year Two |  |  | 0 |  |
Year Three |  |  | 0 |  |
Year Five |  |  | 60 |  |
Prior |  |  | 163 |  |
Revolving Loans Amortized Cost Basis |  |  | 0 |  |
Revolving Loans Converted to Term |  |  | 0 |  |
Total Loans |  |  | 223 |  |
Consumer mortgage | FICO AB |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 137,493 |  | 137,493 |  | 379,171
Year Two | 364,804 |  | 364,804 |  | 492,806
Year Three | 477,150 |  | 477,150 |  | 218,462
Year Four | 209,566 |  | 209,566 |  | 174,126
Year Five | 165,795 |  | 165,795 |  | 100,560
Prior | 658,924 |  | 658,924 |  | 608,605
Revolving Loans Amortized Cost Basis | 369 |  | 369 |  | 954
Revolving Loans Converted to Term | 73,500 |  | 73,500 |  | 59,088
Total Loans | 2,087,601 |  | 2,087,601 |  | 2,033,772
Consumer mortgage | FICO AB | Performing |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 137,493 |  | 137,493 |  | 379,171
Year Two | 364,720 |  | 364,720 |  | 492,731
Year Three | 476,589 |  | 476,589 |  | 217,889
Year Four | 208,994 |  | 208,994 |  | 173,942
Year Five | 165,668 |  | 165,668 |  | 100,161
Prior | 654,032 |  | 654,032 |  | 604,258
Revolving Loans Amortized Cost Basis | 369 |  | 369 |  | 954
Revolving Loans Converted to Term | 73,298 |  | 73,298 |  | 58,639
Total Loans | 2,081,163 |  | 2,081,163 |  | 2,027,745
Consumer mortgage | FICO AB | Nonperforming |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 0 |  | 0 |  | 0
Year Two | 84 |  | 84 |  | 75
Year Three | 561 |  | 561 |  | 573
Year Four | 572 |  | 572 |  | 184
Year Five | 127 |  | 127 |  | 399
Prior | 4,892 |  | 4,892 |  | 4,347
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 0
Revolving Loans Converted to Term | 202 |  | 202 |  | 449
Total Loans | 6,438 |  | 6,438 |  | 6,027
Consumer mortgage | FICO CDE |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 46,030 |  | 46,030 |  | 160,508
Year Two | 158,597 |  | 158,597 |  | 179,236
Year Three | 173,687 |  | 173,687 |  | 113,890
Year Four | 109,206 |  | 109,206 |  | 80,963
Year Five | 77,186 |  | 77,186 |  | 56,988
Prior | 367,826 |  | 367,826 |  | 336,366
Revolving Loans Amortized Cost Basis | 25,942 |  | 25,942 |  | 28,035
Revolving Loans Converted to Term | 26,015 |  | 26,015 |  | 22,717
Total Loans | 984,489 |  | 984,489 |  | 978,703
Consumer mortgage | FICO CDE | Performing |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 46,030 |  | 46,030 |  | 160,388
Year Two | 157,526 |  | 157,526 |  | 178,262
Year Three | 172,772 |  | 172,772 |  | 112,640
Year Four | 107,913 |  | 107,913 |  | 79,357
Year Five | 75,598 |  | 75,598 |  | 54,861
Prior | 353,047 |  | 353,047 |  | 323,189
Revolving Loans Amortized Cost Basis | 25,942 |  | 25,942 |  | 27,884
Revolving Loans Converted to Term | 25,005 |  | 25,005 |  | 22,056
Total Loans | 963,833 |  | 963,833 |  | 958,637
Consumer mortgage | FICO CDE | Nonperforming |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 0 |  | 0 |  | 120
Year Two | 1,071 |  | 1,071 |  | 974
Year Three | 915 |  | 915 |  | 1,250
Year Four | 1,293 |  | 1,293 |  | 1,606
Year Five | 1,588 |  | 1,588 |  | 2,127
Prior | 14,779 |  | 14,779 |  | 13,177
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 151
Revolving Loans Converted to Term | 1,010 |  | 1,010 |  | 661
Total Loans | 20,656 |  | 20,656 |  | 20,066
Consumer indirect |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 383,788 |  | 383,788 |  | 777,531
Year Two | 674,476 |  | 674,476 |  | 422,595
Year Three | 342,821 |  | 342,821 |  | 129,502
Year Four | 97,131 |  | 97,131 |  | 99,660
Year Five | 68,205 |  | 68,205 |  | 52,313
Prior | 78,390 |  | 78,390 |  | 58,052
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total Loans | 1,644,811 |  | 1,644,811 |  | 1,539,653
Year One |  |  | 85 |  |
Year Two |  |  | 1,656 |  |
Year Three |  |  | 1,064 |  |
Year Four |  |  | 603 |  |
Year Five |  |  | 364 |  |
Prior |  |  | 618 |  |
Revolving Loans Amortized Cost Basis |  |  | 0 |  |
Revolving Loans Converted to Term |  |  | 0 |  |
Total Loans |  |  | 4,390 |  |
Consumer indirect | Performing |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 383,788 |  | 383,788 |  | 777,513
Year Two | 674,381 |  | 674,381 |  | 422,594
Year Three | 342,764 |  | 342,764 |  | 129,449
Year Four | 97,123 |  | 97,123 |  | 99,593
Year Five | 68,195 |  | 68,195 |  | 52,298
Prior | 78,364 |  | 78,364 |  | 58,028
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total Loans | 1,644,615 |  | 1,644,615 |  | 1,539,475
Consumer indirect | Nonperforming |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 0 |  | 0 |  | 18
Year Two | 95 |  | 95 |  | 1
Year Three | 57 |  | 57 |  | 53
Year Four | 8 |  | 8 |  | 67
Year Five | 10 |  | 10 |  | 15
Prior | 26 |  | 26 |  | 24
Revolving Loans Amortized Cost Basis | 0 |  | 0 |  | 0
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total Loans | 196 |  | 196 |  | 178
Consumer direct |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 45,181 |  | 45,181 |  | 84,117
Year Two | 66,184 |  | 66,184 |  | 46,432
Year Three | 35,417 |  | 35,417 |  | 17,067
Year Four | 12,163 |  | 12,163 |  | 12,730
Year Five | 8,041 |  | 8,041 |  | 5,602
Prior | 7,372 |  | 7,372 |  | 5,070
Revolving Loans Amortized Cost Basis | 6,626 |  | 6,626 |  | 6,585
Revolving Loans Converted to Term | 1 |  | 1 |  | 2
Total Loans | 180,985 |  | 180,985 |  | 177,605
Year One |  |  | 14 |  |
Year Two |  |  | 302 |  |
Year Three |  |  | 227 |  |
Year Four |  |  | 32 |  |
Year Five |  |  | 51 |  |
Prior |  |  | 98 |  |
Revolving Loans Amortized Cost Basis |  |  | 88 |  |
Revolving Loans Converted to Term |  |  | 0 |  |
Total Loans |  |  | 812 |  |
Consumer direct | Performing |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 45,181 |  | 45,181 |  | 84,111
Year Two | 66,175 |  | 66,175 |  | 46,381
Year Three | 35,407 |  | 35,407 |  | 17,066
Year Four | 12,163 |  | 12,163 |  | 12,729
Year Five | 8,041 |  | 8,041 |  | 5,573
Prior | 7,291 |  | 7,291 |  | 5,020
Revolving Loans Amortized Cost Basis | 6,622 |  | 6,622 |  | 6,563
Revolving Loans Converted to Term | 1 |  | 1 |  | 2
Total Loans | 180,881 |  | 180,881 |  | 177,445
Consumer direct | Nonperforming |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 0 |  | 0 |  | 6
Year Two | 9 |  | 9 |  | 51
Year Three | 10 |  | 10 |  | 1
Year Four | 0 |  | 0 |  | 1
Year Five | 0 |  | 0 |  | 29
Prior | 81 |  | 81 |  | 50
Revolving Loans Amortized Cost Basis | 4 |  | 4 |  | 22
Revolving Loans Converted to Term | 0 |  | 0 |  | 0
Total Loans | 104 |  | 104 |  | 160
Home equity |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 31,517 |  | 31,517 |  | 69,575
Year Two | 66,814 |  | 66,814 |  | 72,280
Year Three | 67,801 |  | 67,801 |  | 38,078
Year Four | 34,747 |  | 34,747 |  | 31,675
Year Five | 28,693 |  | 28,693 |  | 16,173
Prior | 50,877 |  | 50,877 |  | 41,703
Revolving Loans Amortized Cost Basis | 128,571 |  | 128,571 |  | 133,266
Revolving Loans Converted to Term | 30,166 |  | 30,166 |  | 31,246
Total Loans | 439,186 |  | 439,186 |  | 433,996
Year One |  |  | 0 |  |
Year Two |  |  | 0 |  |
Year Three |  |  | 0 |  |
Year Four |  |  | 64 |  |
Year Five |  |  | 0 |  |
Prior |  |  | 8 |  |
Revolving Loans Amortized Cost Basis |  |  | 8 |  |
Revolving Loans Converted to Term |  |  | 4 |  |
Total Loans |  |  | 84 |  |
Home equity | Performing |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 31,517 |  | 31,517 |  | 69,575
Year Two | 66,814 |  | 66,814 |  | 72,270
Year Three | 67,791 |  | 67,791 |  | 37,964
Year Four | 34,430 |  | 34,430 |  | 31,506
Year Five | 28,516 |  | 28,516 |  | 16,068
Prior | 50,268 |  | 50,268 |  | 41,097
Revolving Loans Amortized Cost Basis | 127,840 |  | 127,840 |  | 132,703
Revolving Loans Converted to Term | 29,648 |  | 29,648 |  | 30,569
Total Loans | 436,824 |  | 436,824 |  | 431,752
Home equity | Nonperforming |  |  |  |  |
Term loans amortized cost basis by origination year |  |  |  |  |
Year One | 0 |  | 0 |  | 0
Year Two | 0 |  | 0 |  | 10
Year Three | 10 |  | 10 |  | 114
Year Four | 317 |  | 317 |  | 169
Year Five | 177 |  | 177 |  | 105
Prior | 609 |  | 609 |  | 606
Revolving Loans Amortized Cost Basis | 731 |  | 731 |  | 563
Revolving Loans Converted to Term | 518 |  | 518 |  | 677
Total Loans | $ 2,362 |  | $ 2,362 |  | $ 2,244

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

X
- Definition Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-13 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestAllowanceForCreditLossWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amortized cost excluding accrued interest, before allowance for credit loss, of financing receivable. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479344/326-20-45-1 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3B -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 5 -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-5 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestBeforeAllowanceForCreditLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost excluding accrued interest, of financing receivable originated more than five years prior to current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3B -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, excluding accrued interest, of writeoff of financing receivable originated more than five years before current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestOriginatedMoreThanFiveYearsBeforeCurrentFiscalYearWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amortized cost excluding accrued interest, of financing receivable that can be withdrawn, repaid, and redrawn. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3B -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestRevolving
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amortized cost excluding accrued interest, of revolving financing receivable converted to term loan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6A -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6A Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3B -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoan
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, excluding accrued interest, of writeoff of revolving financing receivable converted to term loan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6A -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6A + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingConvertedToTermLoanWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount, excluding accrued interest, of writeoff of financing receivable that can be withdrawn, repaid, and redrawn. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestRevolvingWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amortized cost excluding accrued interest, of financing receivable originated four years prior to current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3B -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, excluding accrued interest, of writeoff of financing receivable originated four years before current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestYearFiveOriginatedFourYearsBeforeCurrentFiscalYearWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amortized cost excluding accrued interest, of financing receivable originated three years prior to current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3B -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, excluding accrued interest, of writeoff of financing receivable originated three years before current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestYearFourOriginatedThreeYearsBeforeCurrentFiscalYearWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amortized cost excluding accrued interest, of financing receivable originated in current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3B -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, excluding accrued interest, of writeoff of financing receivable originated in current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestYearOneOriginatedCurrentFiscalYearWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amortized cost excluding accrued interest, of financing receivable originated two years prior to current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3B -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, excluding accrued interest, of writeoff of financing receivable originated two years before current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestYearThreeOriginatedTwoYearsBeforeCurrentFiscalYearWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amortized cost excluding accrued interest of financing receivable originated in fiscal year prior to current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 55 -Paragraph 79 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479294/326-20-55-79 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 3B -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-3B + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, excluding accrued interest, of writeoff of financing receivable originated in fiscal year before current fiscal year. Excludes net investment in lease. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-6 + Details
Name: | us-gaap_FinancingReceivableExcludingAccruedInterestYearTwoOriginatedFiscalYearBeforeCurrentFiscalYearWriteoff
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=cbu_LegacyLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialLoanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_PassMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_SpecialMentionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_SubstandardMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=us-gaap_DoubtfulMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialMortgageMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditScoreFicoAxis=cbu_FICOScoreGreaterThanOrEqualTo720Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_PerformingFinancingReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_NonperformingFinancingReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CreditScoreFicoAxis=cbu_FICOScoreLessThan720Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=cbu_ConsumerInstallmentIndirectMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=cbu_ConsumerInstallmentDirectMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=cbu_HomeEquityReceivablesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |