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Employee Benefits - Weighted-average assumptions used to determine future benefit obligations (Details) - Pension Plan | Dec. 31, 2020 | Dec. 31, 2019
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U.K. |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Discount rate | 1.45% | 2.09%
Underlying price inflation | 2.12% | 1.78%
U.K. | Minimum |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Rate of compensation increase | 3.22% | 3.24%
U.K. | Maximum |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Rate of compensation increase | 3.72% | 3.74%
U.S. | Minimum |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Discount rate | 1.74% | 2.72%
U.S. | Maximum |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Discount rate | 2.45% | 3.17%
Other |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Underlying price inflation | 2.00% | 2.00%
Other | Minimum |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Discount rate | 0.38% | 0.91%
Rate of compensation increase | 1.00% | 1.00%
Other | Maximum |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Discount rate | 2.47% | 3.10%
Rate of compensation increase | 3.00% | 3.00%

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- Definition Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Underlying Price Inflation + References No definition available. + Details
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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 + Details
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- Definition Weighted average rate increase of compensation, used to determine benefit obligation 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 + Details
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- Definition 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. + References No definition available. + Details
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