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BENEFIT PLANS (Tables) | 12 Months Ended
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Dec. 31, 2021
BENEFIT PLANS |
Schedule of funded status of the Company???s plans reconciled with amounts reported | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Pension Benefits | ​ | Post-retirement Benefits
(000’s omitted) |  | 2021 |  | 2020 |  | 2021 |  | 2020
Change in benefit obligation: |  | ​ |  |  | ​ |  |  | ​ |  |  | ​ |
Benefit obligation at the beginning of year | ​ | $ | 190,361 | ​ | $ | 162,084 | ​ | $ | 1,718 | ​ | $ | 1,677
Service cost | ​ |  | 5,920 | ​ |  | 5,750 | ​ |  | 0 | ​ |  | 0
Interest cost | ​ |  | 5,036 | ​ |  | 5,657 | ​ |  | 44 | ​ |  | 57
Plan amendment / acquisition | ​ |  | 0 | ​ |  | 13,598 | ​ |  | 0 | ​ |  | 0
Participant contributions | ​ |  | 0 | ​ |  | 0 | ​ |  | 0 | ​ |  | 0
Deferred actuarial (gain)/loss | ​ |  | (4,881) | ​ |  | 13,954 | ​ |  | (85) | ​ |  | 114
Benefits paid | ​ |  | (13,166) | ​ |  | (10,682) | ​ |  | (148) | ​ |  | (130)
Benefit obligation at end of year | ​ |  | 183,270 | ​ |  | 190,361 | ​ |  | 1,529 | ​ |  | 1,718
Change in plan assets: | ​ |  | ​ | ​ |  | ​ | ​ |  | ​ | ​ |  | ​
Fair value of plan assets at beginning of year | ​ |  | 272,600 | ​ |  | 227,323 | ​ |  | 0 | ​ |  | 0
Actual return of plan assets | ​ |  | 27,614 | ​ |  | 33,543 | ​ |  | 0 | ​ |  | 0
Participant contributions | ​ |  | 0 | ​ |  | 0 | ​ |  | 0 | ​ |  | 0
Employer contributions | ​ |  | 3,639 | ​ |  | 7,993 | ​ |  | 148 | ​ |  | 130
Plan acquisition | ​ |  | 0 | ​ |  | 14,423 | ​ |  | 0 | ​ |  | 0
Benefits paid | ​ |  | (13,166) | ​ |  | (10,682) | ​ |  | (148) | ​ |  | (130)
Fair value of plan assets at end of year | ​ |  | 290,687 | ​ |  | 272,600 | ​ |  | 0 | ​ |  | 0
Over/(Under) funded status at year end | ​ | $ | 107,417 | ​ | $ | 82,239 | ​ | $ | (1,529) | ​ | $ | (1,718)
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
Amounts recognized in the consolidated statement of condition were: | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |
Other assets | ​ | $ | 127,538 | ​ | $ | 101,849 | ​ | $ | 0 | ​ | $ | 0
Other liabilities | ​ |  | (20,121) | ​ |  | (19,610) | ​ |  | (1,529) | ​ |  | (1,718)
Amounts recognized in accumulated other comprehensive loss/(income) (“AOCI”) were: | ​ |  |  | ​ |  |  | ​ |  |  | ​ |  |
Net loss | ​ | $ | 16,977 | ​ | $ | 34,290 | ​ | $ | 585 | ​ | $ | 715
Net prior service cost (credit) | ​ |  | 3,969 | ​ |  | 4,348 | ​ |  | (907) | ​ |  | (1,086)
Pre-tax AOCI | ​ |  | 20,946 | ​ |  | 38,638 | ​ |  | (322) | ​ |  | (371)
Taxes | ​ |  | (5,236) | ​ |  | (9,488) | ​ |  | 82 | ​ |  | 94
AOCI at year end | ​ | $ | 15,710 | ​ | $ | 29,150 | ​ | $ | (240) | ​ | $ | (277)
Schedule of Amounts recognized in accumulated other comprehensive income, net of tax | Amounts recognized in accumulated other comprehensive income, net of tax, for the year ended December 31, are as follows: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Pension Benefits | ​ | Post-retirement Benefits
(000’s omitted) |  | 2021 |  | 2020 |  | 2021 |  | 2020
Prior service cost/(credit) | ​ | $ | (288) | ​ | $ | 222 | ​ | $ | 136 | ​ | $ | 136
Net (gain) loss | ​ |  | (13,152) | ​ |  | (6,423) | ​ |  | (99) | ​ |  | 56
Total | ​ | $ | (13,440) | ​ | $ | (6,201) | ​ | $ | 37 | ​ | $ | 192
​
Schedule of weighted-average assumptions used to determine the benefit obligations | ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Pension Benefits | ​ | Post-retirement Benefits |
​ |  | 2021 |  | 2020 |  | 2021 |  | 2020 |
Discount rate |  | 3.10 | % | 2.80 | % | 3.10 | % | 2.80 | %
Expected return on plan assets |  | 6.70 | % | 7.00 | % | N/A |  | N/A | ​
Rate of compensation increase | ​ | 4.00% for 2022 | ​ | 3.50 | % | N/A | ​ | N/A | ​
​ |  | 3.50% for 2023 | + | ​ | ​ | ​ |  | ​ | ​
Interest crediting rates | ​ | 6.00% while employed, | ​ | 6.00% while employed, | ​ | N/A | ​ | N/A | ​
​ | ​ | 1.94% after termination | ​ | 1.42% after termination | ​ | ​ | ​ | ​ | ​
​
Schedule of net periodic benefit cost | The net periodic benefit cost as of December 31 is as follows: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Pension Benefits | ​ | Post-retirement Benefits
(000’s omitted) |  | 2021 |  | 2020 |  | 2019 |  | 2021 |  | 2020 |  | 2019
Service cost | ​ | $ | 5,920 | ​ | $ | 5,750 | ​ | $ | 5,081 | ​ | $ | 0 | ​ | $ | 0 | ​ | $ | 0
Interest cost | ​ |  | 5,036 | ​ |  | 5,657 | ​ |  | 6,264 | ​ |  | 44 | ​ |  | 57 | ​ |  | 70
Expected return on plan assets | ​ |  | (18,783) | ​ |  | (16,306) | ​ |  | (14,311) | ​ |  | 0 | ​ |  | 0 | ​ |  | 0
Plan amendment | ​ |  | 0 | ​ |  | (637) | ​ |  | 0 | ​ |  | 0 | ​ |  | 0 | ​ |  | 0
Amortization of unrecognized net loss | ​ |  | 3,600 | ​ |  | 3,239 | ​ |  | 2,568 | ​ |  | 45 | ​ |  | 40 | ​ |  | 38
Amortization of prior service cost | ​ |  | 379 | ​ |  | 241 | ​ |  | 64 | ​ |  | (179) | ​ |  | (179) | ​ |  | (179)
Net periodic (benefit) | ​ | $ | (3,848) | ​ | $ | 2,056 | ​ | $ | (334) | ​ | $ | (90) | ​ | $ | (82) | ​ | $ | (71)
​
Schedule of weighted-average assumptions used to determine the net periodic pension cost | The weighted-average assumptions used to determine the net periodic pension cost for the years ended December 31 are as follows: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Pension Benefits | ​ | Post-retirement Benefits |
​ |  | 2021 |  | 2020 |  | 2019 |  | 2021 |  | 2020 |  | 2019 |
Discount rate |  | 2.80 | % | 3.50 | % | 4.50 | % | 2.80 | % | 3.60 | % | 4.45 | %
Expected return on plan assets |  | 7.00 | % | 7.00 | % | 7.00 | % | N/A |  | N/A |  | N/A | ​
Rate of compensation increase |  | 3.50 | % | 3.50 | % | 3.50 | % | N/A |  | N/A |  | N/A | ​
Interest crediting rates | ​ | 6.00% while employed, | ​ | 6.00% while employed | ​ | 6.00% while employed | ​ | N/A | ​ | N/A | ​ | N/A | ​
​ | ​ | 1.42% after termination | ​ | 2.16% after termination | ​ | 3.15% after termination | ​ | ​ | ​ | ​ | ​ | ​ | ​
Schedule of amount of benefit payments | The amount of benefit payments that are expected to be paid over the next ten years are as follows: ​
​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | ​ | Pension | ​ | ​ | Post-retirement
(000’s omitted) |  | ​ | Benefits |  | ​ | Benefits
2022 | ​ | $ | 10,940 | ​ | $ | 151
2023 | ​ |  | 11,863 | ​ |  | 119
2024 | ​ |  | 12,185 | ​ |  | 117
2025 | ​ |  | 11,991 | ​ |  | 115
2026 | ​ |  | 13,567 | ​ |  | 113
2027-2031 | ​ |  | 63,874 | ​ |  | 522
​
Schedule of fair value of defined benefit plan assets by asset category | The fair values of the Company’s defined benefit pension plan assets at December 31, 2021 by asset category are as follows: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Quoted Prices | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | in Active | ​ | Significant | ​ | Significant | ​ |  | ​
​ | ​ | Markets for | ​ | Observable | ​ | Unobservable | ​ |  | ​
​ | ​ | Identical Assets | ​ | Inputs | ​ | Inputs | ​ |  | ​
Asset category (000’s omitted) |  | Level 1 |  | Level 2 |  | Level 3 |  | Total
Cash equivalents | ​ | $ | 19,605 | ​ | $ | 0 | ​ | $ | 0 | ​ | $ | 19,605
Equity securities: | ​ |  | ​ | ​ |  | ​ | ​ |  |  | ​ |  | ​
U.S. large-cap | ​ |  | 75,180 | ​ |  | 0 | ​ |  | 0 | ​ |  | 75,180
U.S mid/small cap | ​ |  | 12,052 | ​ |  | 0 | ​ |  | 0 | ​ |  | 12,052
CBU common stock | ​ |  | 7,604 | ​ |  | 0 | ​ |  | 0 | ​ |  | 7,604
International | ​ |  | 73,891 | ​ |  | 0 | ​ |  | 0 | ​ |  | 73,891
Other | ​ |  | 1,091 | ​ |  | 0 | ​ |  | 0 | ​ |  | 1,091
​ | ​ |  | 169,818 | ​ |  | 0 | ​ |  | 0 | ​ |  | 169,818
​ | ​ |  | ​ | ​ |  | ​ | ​ |  |  | ​ |  | ​
Fixed income securities: | ​ |  | ​ | ​ |  | ​ | ​ |  |  | ​ |  | ​
Government securities | ​ |  | 19,988 | ​ |  | 5,974 | ​ |  | 0 | ​ |  | 25,962
Investment grade bonds | ​ |  | 41,374 | ​ |  | 136 | ​ |  | 0 | ​ |  | 41,510
High yield(a) | ​ |  | 8,625 | ​ |  | 0 | ​ |  | 0 | ​ |  | 8,625
​ | ​ |  | 69,987 | ​ |  | 6,110 | ​ |  | 0 | ​ |  | 76,097
​ | ​ |  | ​ | ​ |  | ​ | ​ |  |  | ​ |  | ​
Other investments (b) | ​ |  | 24,727 | ​ |  | 0 | ​ |  | 0 | ​ |  | 24,727
​ | ​ |  | ​ | ​ |  | ​ | ​ |  |  | ​ |  | ​
Total (c) | ​ | $ | 284,137 | ​ | $ | 6,110 | ​ | $ | 0 | ​ | $ | 290,247
​ The fair values of the Company’s defined benefit pension plan assets at December 31, 2020 by asset category are as follows: ​
​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | Quoted Prices | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​ | ​
​ | ​ | in Active | ​ | Significant | ​ | Significant | ​ | ​ | ​
​ | ​ | Markets for | ​ | Observable | ​ | Unobservable | ​ | ​ | ​
​ | ​ | Identical Assets | ​ | Inputs | ​ | Inputs | ​ | ​ | ​
Asset category (000’s omitted) |  | Level 1 |  | Level 2 |  | Level 3 |  | Total
Cash equivalents | ​ | $ | 68,137 | ​ | $ | 0 | ​ | $ | 0 | ​ | $ | 68,137
Equity securities: | ​ |  | ​ | ​ |  | ​ | ​ |  |  | ​ |  | ​
U.S. large-cap | ​ |  | 69,195 | ​ |  | 0 | ​ |  | 0 | ​ |  | 69,195
U.S mid/small cap | ​ |  | 17,338 | ​ |  | 0 | ​ |  | 0 | ​ |  | 17,338
CBU common stock | ​ |  | 7,701 | ​ |  | 0 | ​ |  | 0 | ​ |  | 7,701
International | ​ |  | 43,457 | ​ |  | 6,088 | ​ |  | 0 | ​ |  | 49,545
​ | ​ |  | 137,691 | ​ |  | 6,088 | ​ |  | 0 | ​ |  | 143,779
​ | ​ |  | ​ | ​ |  | ​ | ​ |  |  | ​ |  | ​
Fixed income securities: | ​ |  | ​ | ​ |  | ​ | ​ |  |  | ​ |  | ​
Government securities | ​ |  | 6,154 | ​ |  | 6,241 | ​ |  | 0 | ​ |  | 12,395
Investment grade bonds | ​ |  | 23,085 | ​ |  | 141 | ​ |  | 0 | ​ |  | 23,226
High yield(a) | ​ |  | 5,803 | ​ |  | 0 | ​ |  | 0 | ​ |  | 5,803
​ | ​ |  | 35,042 | ​ |  | 6,382 | ​ |  | 0 | ​ |  | 41,424
​ | ​ |  | ​ | ​ |  | ​ | ​ |  |  | ​ |  | ​
Other investments (b) | ​ |  | 17,613 | ​ |  | 0 | ​ |  | 0 | ​ |  | 17,613
​ | ​ |  | ​ | ​ |  | ​ | ​ |  |  | ​ |  | ​
Total (c)(d) | ​ | $ | 258,483 | ​ | $ | 12,470 | ​ | $ | 0 | ​ | $ | 270,953
​
(a) | This category is exchange-traded funds representing a diversified index of high yield corporate bonds.
(b) | This category is comprised of exchange-traded funds and mutual funds holding non-traditional investment classes including private equity funds and alternative exchange funds.
(c) | Excludes dividends and interest receivable totaling $0.4 million and $0.2 million at December 31, 2021 and 2020, respectively.
(d) | Excludes certain investments that were measured at net asset value per share (or its equivalents) totaling $1.4 million at December 31, 2020.

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