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Postretirement Health Care and Life Insurance Benefits - Assumptions Used to Determine the Benefit Obligations and Periodic Benefit Cost (Details) | 12 Months Ended
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Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Postretirement Health Care and Life Insurance Benefits |  |  |
Weighted-average assumptions used to determine benefit obligations |  |  |
Discount rate | 2.84% | 2.55% |
Weighted-average assumptions used to determine net periodic benefit cost |  |  |
Discount rate | 2.55% | 3.40% | 4.35%
Expected long-term return on plan assets (pre-tax) | 5.75% | 7.00% | 5.00%
Postretirement Health Care and Life Insurance Benefits | Maximum |  |  |
Weighted-average assumptions used to determine net periodic benefit cost |  |  |
Expected long-term return on plan assets (pre-tax) | 5.75% |  |
Pre-Medicare |  |  |
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract] |  |  |
Health care cost trend rate assumed for next year | 6.00% | 6.00% |
Rate to which the cost trend is assumed to decline (the ultimate trend rate) | 4.75% | 4.75% |
Post-Medicare |  |  |
Defined Benefit Plan, Assumed Health Care Cost Trend Rates [Abstract] |  |  |
Health care cost trend rate assumed for next year | 5.75% | 5.75% |
Rate to which the cost trend is assumed to decline (the ultimate trend rate) | 4.75% | 4.75% |

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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=123447040&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=123447040&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=123447040&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=123447040&loc=d3e2919-114920 + Details
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- Definition Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status. + 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 (l) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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- Definition Ultimate trend rate for health care cost for defined benefit postretirement 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 (l) -URI http://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920 + Details
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