Retirement Plans and Other Postretirement Benefits - Asset Allocation (Details)	Dec. 31, 2020
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	100.00%
Actual Allocation	100.00%
Pension Benefits \| Long-term fixed income assets
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	72.00%
Actual Allocation	68.00%
Pension Benefits \| Return-generating assets
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	28.00%
Actual Allocation	32.00%
Target Allocation	28.00%
Pension Benefits \| Equities in US and other developed markets
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	17.00%
Pension Benefits \| Equities in emerging markets
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	6.00%
Pension Benefits \| Alternative investments
Defined Benefit Plan Disclosure [Line Items]
Target Allocation	5.00%
Other Benefits
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation	100.00%
Other Benefits \| Long-term fixed income assets
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation	55.00%
Other Benefits \| Return-generating assets
Defined Benefit Plan Disclosure [Line Items]
Actual Allocation	45.00%

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- Definition

Percentage of investment to total investment within defined benefit plan asset category.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(ii)
-URI http://asc.fasb.org/extlink&oid=118255775&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=118257860&loc=d3e4179-114921

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- Definition

Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

+ 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=118257860&loc=d3e4179-114921

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(i)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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Percentage of actual investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan.

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