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Retirement Plans - Schedule of Weighted Average Assets Allocation and Weighted Average Target Allocation (Details) - United Kingdom Subsidiary - UK Plan | Dec. 31, 2020 | Dec. 31, 2019
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Defined Benefit Plan Disclosure [Line Items] |  |
Target Asset Allocation | 100.00% |
Asset Allocation | 100.00% | 100.00%
Debt |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target Asset Allocation | 65.00% |
Asset Allocation | 63.00% | 70.60%
Equity |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target Asset Allocation | 15.00% |
Asset Allocation | 12.70% | 10.50%
Cash |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target Asset Allocation | 10.00% |
Asset Allocation | 17.10% | 10.50%
Real estate |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target Asset Allocation | 10.00% |
Asset Allocation | 7.20% | 8.40%

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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 + Details
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