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Retirement Plans and Other Benefits - Asset Allocation (Details) | Dec. 31, 2017
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Pension Benefits |
Defined Benefit Plan Disclosure [Line Items] |
Target allocation (as a percent) | 100.00%
Actual asset allocation (as a percent) | 100.00%
Pension Benefits | Fixed income securities |
Defined Benefit Plan Disclosure [Line Items] |
Target allocation (as a percent) | 62.00%
Actual asset allocation (as a percent) | 58.00%
Pension Benefits | Return-generating assets |
Defined Benefit Plan Disclosure [Line Items] |
Target allocation (as a percent) | 38.00%
Actual asset allocation (as a percent) | 42.00%
Pension Benefits | Equities in US and other developed markets |
Defined Benefit Plan Disclosure [Line Items] |
Target allocation (as a percent) | 18.00%
Pension Benefits | Equities in emerging markets |
Defined Benefit Plan Disclosure [Line Items] |
Target allocation (as a percent) | 6.00%
Pension Benefits | Alternative investments |
Defined Benefit Plan Disclosure [Line Items] |
Target allocation (as a percent) | 14.00%
Other Benefits |
Defined Benefit Plan Disclosure [Line Items] |
Actual asset allocation (as a percent) | 100.00%
Other Benefits | Fixed income securities |
Defined Benefit Plan Disclosure [Line Items] |
Actual asset allocation (as a percent) | 67.00%
Other Benefits | Return-generating assets |
Defined Benefit Plan Disclosure [Line Items] |
Actual asset allocation (as a percent) | 33.00%

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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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(5)(i) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2446-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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