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Pensions and Other Postretirement Benefits - Benefit Assumptions (Details) | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Return on assets in plans | 8.00% |  |
Funded Plan | Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate | 2.67% | 3.38% | 4.33%
Future salary increases | 4.21% | 4.21% | 4.21%
Funded Plan | OPEB |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate | 2.27% | 3.13% | 4.18%
Unfunded Plan | Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Future salary increases | 4.21% | 4.21% | 4.21%
Discount rate for service cost | 3.71% | 4.55% | 4.01%
Discount rate for interest cost | 2.92% | 3.99% | 3.33%
Return on assets in plans | 8.25% | 8.25% | 8.25%
Unfunded Plan | OPEB |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate for service cost | 3.41% | 4.39% | 3.83%
Discount rate for interest cost | 2.69% | 3.83% | 3.13%
Return on assets in plans | 8.00% | 8.00% | 8.00%
Health care trend rate | 6.25% | 6.50% | 6.30%

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- Definition Defined Benefit Plan Assumed Health Care Cost Trend Rate + References No definition available. + Details
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- Definition Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate For Interest Cost + References No definition available. + Details
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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 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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- Definition Weighted average rate of compensation increase used to determine net periodic benefit cost of defined benefit plan. Plan includes, but is not limited to, pay-related 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)(2) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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