Pension and Postretirement Benefits - Weighted Average Asset Allocations and Target Asset Allocations by Asset Category (Details)	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Asset Allocations (as a percent)	100.00%	100.00%
Target Asset Allocations (as a percent)	100.00%	100.00%
Return-Seeking assets
Defined Benefit Plan Disclosure [Line Items]
Asset Allocations (as a percent)	58.00%	59.00%
Target Asset Allocations (as a percent)	56.00%	56.00%
Liability-Hedging assets
Defined Benefit Plan Disclosure [Line Items]
Asset Allocations (as a percent)	42.00%	41.00%
Target Asset Allocations (as a percent)	44.00%	44.00%

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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.

+ 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)(i)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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