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PENSION AND OTHER POSTRETIREMENT PLANS (Schedule of Assumptions Used in Calculating the Net Benefit Obligation) (Details) | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Pension Benefits |  |  |
Defined Benefit Plan Disclosure |  |  |
Net benefit obligation, Weighted average discount rate | 2.08% | 2.98% | 4.08%
Lump sum assumed interest rates for First 5 years | 0.53% | 2.01% | 3.33%
Lump sum assumed interest rates for Next 15 years | 2.31% | 3.06% | 4.39%
Lump sum assumed interest rates for All future years | 3.09% | 3.65% | 4.72%
Net pension expense, Weighted average discount rate | 2.98% | 4.08% | 3.46%
Expected long-term rate of return | 6.50% | 6.50% | 6.50%
SERP Benefits |  |  |
Defined Benefit Plan Disclosure |  |  |
Net benefit obligation, Weighted average discount rate | 2.08% | 2.98% | 4.08%
Net pension expense, Weighted average discount rate | 2.98% | 4.08% | 3.46%
Expected long-term rate of return | 6.50% | 6.50% | 6.50%

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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of 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 (k)(1) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of 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 (k)(1) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of 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 (k)(3) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2919-114920 + Details
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