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Pensions and Other Postretirement Benefits - Benefit Assumptions (Details)	12 Months Ended
	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%

X

- Definition

Defined Benefit Plan Assumed Health Care Cost Trend Rate

+ References

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- Definition

Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate For Interest Cost

+ References

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- Definition

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+ References

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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

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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

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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

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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