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Pension Benefits - Weighted Average Asset Allocation for Pension Plans (Details) - Pension Plans, Defined Benefit | Dec. 31, 2020 | Dec. 31, 2019
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Defined Benefit Plan Disclosure [Line Items] |  |
Weighted-average asset allocations | 100.00% | 100.00%
Corporate Bonds and Notes |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted-average asset allocations | 37.00% | 40.00%
Common and Preferred Stocks |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted-average asset allocations | 24.00% | 35.00%
Bond Exchange Traded Funds |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted-average asset allocations | 27.00% | 14.00%
Cash and Short-term Investments |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted-average asset allocations | 2.00% | 2.00%
Other Assets |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted-average asset allocations | 10.00% | 9.00%

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- Definition 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 + Details
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