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RETIREMENT AND POSTRETIREMENT PLANS - Funded status of the Employee Retirement Plan (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Retirement Plans [Member] |  |  |
Reconciliation of projected benefit obligation: |  |  |
Acquired in the Merger | $ 33,897 |  |
Service cost | 893 |  |
Interest cost | 609 |  |
Actuarial gain | (304) |  |
Benefit payments | (600) |  |
Projected benefit obligation at end of year | 34,495 |  |
Plan assets at fair value (investments in trust funds managed by trustee) |  |  |
Acquired in the Merger | 43,685 |  |
Return on plan assets | 4,772 |  |
Benefit payments | (600) |  |
Balance at end of year | 47,857 |  |
Funded status at end of year | 13,362 |  |
Employee Retirement Plan |  |  |
Reconciliation of projected benefit obligation: |  |  |
Projected benefit obligation at beginning of year | 26,891 | $ 25,405 |
Interest cost | 562 | 732 | $ 901
Actuarial gain | (903) | 2,204 |
Benefit payments | (1,589) | (1,450) |
Projected benefit obligation at end of year | 24,961 | 26,891 | 25,405
Plan assets at fair value (investments in trust funds managed by trustee) |  |  |
Balance at beginning of year | 27,142 | 25,202 |
Return on plan assets | 3,140 | 3,390 |
Benefit payments | (1,589) | (1,450) |
Balance at end of year | 28,693 | 27,142 | 25,202
Funded status at end of year | 3,732 | 251 |
RETIREMENT PLANS | BMP and Outside Director Retirement Plan |  |  |
Reconciliation of projected benefit obligation: |  |  |
Projected benefit obligation at beginning of year | 9,328 | 9,360 |
Interest cost | 12 | 234 | 351
Actuarial gain | (277) | 505 |
Benefit payments | (9,063) | (771) |
Projected benefit obligation at end of year |  | 9,328 | 9,360
Plan assets at fair value (investments in trust funds managed by trustee) |  |  |
Contributions | 9,063 | 771 |
Benefit payments | (9,063) | (771) |
Funded status at end of year |  | (9,328) |
POSTRETIREMENT PLANS |  |  |
Reconciliation of projected benefit obligation: |  |  |
Projected benefit obligation at beginning of year | 13 | 1,608 |
Interest cost |  | 42 | 56
Actuarial gain |  | 105 |
Curtailment gain | (1,600) | (1,577) |
Benefit payments | (13) | (165) |
Projected benefit obligation at end of year |  | 13 | $ 1,608
Plan assets at fair value (investments in trust funds managed by trustee) |  |  |
Contributions | 13 | 165 |
Benefit payments | $ (13) | (165) |
Funded status at end of year |  | $ (13) |

X
- Definition Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921 + Details
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- Definition Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Amount of payment to participant of defined benefit plan which decreases benefit obligation. For pension plan, payment includes, but is not limited to, pension benefits and death benefits. For other postretirement plan, payment includes, but is not limited to, prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(6) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 60 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6414203&loc=d3e39716-114964 + Details
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- Definition Amount of increase in plan assets of defined benefit plan from business combination. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(6) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Amount of contribution received by defined benefit plan from employer which increases plan assets. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e2709-114920 Reference 4: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 5: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=123450688&loc=d3e4587-114921 Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(iv)(01) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(3) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Amount of (increase) decrease in benefit obligation of defined benefit plan from event reducing expected years of future service of present employees or eliminating accrual of benefits for some or all future services of present employees. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(10) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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