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Employee and Retiree Benefit Plans - Weighted Average Asset Allocation for Funded Pension Benefit Plans (Details) | Dec. 31, 2020 | Dec. 31, 2019
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Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 100.00% | 100.00%
Equity securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 58.10% | 54.90%
Fixed income securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 24.00% | 26.20%
Alternatives |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 13.20% | 17.30%
Cash and equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 4.70% | 1.60%
Domestic Plan | Equity securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 56.00% |
Domestic Plan | Fixed income securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 28.00% |
Domestic Plan | Alternatives |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 11.40% |
Domestic Plan | Cash and equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 4.60% |
Domestic Plan | Minimum | Equity securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocations of plan assets | 40.00% |
Domestic Plan | Minimum | Fixed income securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocations of plan assets | 28.00% |
Domestic Plan | Minimum | Alternatives |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocations of plan assets | 0.00% |
Domestic Plan | Minimum | Cash and equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocations of plan assets | 0.00% |
Domestic Plan | Maximum | Equity securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocations of plan assets | 70.00% |
Domestic Plan | Maximum | Fixed income securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocations of plan assets | 60.00% |
Domestic Plan | Maximum | Alternatives |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocations of plan assets | 18.00% |
Domestic Plan | Maximum | Cash and equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocations of plan assets | 15.00% |
Canadian Plan | Equity securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 31.00% |
Canadian Plan | Fixed income securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 68.00% |
Canadian Plan | Alternatives |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocations of plan assets | 0.00% |
Weighted average asset allocation | 0.00% |
Canadian Plan | Cash and equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 1.00% |
Canadian Plan | Maximum | Equity securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocations of plan assets | 0.00% |
Canadian Plan | Maximum | Fixed income securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocations of plan assets | 98.00% |
Canadian Plan | Maximum | Cash and equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target allocations of plan assets | 2.00% |
U.K. Plan | Equity securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 65.00% |
U.K. Plan | Fixed income securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 11.70% |
U.K. Plan | Alternatives |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 18.00% |
U.K. Plan | Cash and equivalents |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Weighted average asset allocation | 5.30% |

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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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