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Defined Pension Benefit Obligations - Narrative (Details) $ in Thousands | 1 Months Ended | 3 Months Ended | 9 Months Ended
--- | --- | --- | ---
Jul. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Jun. 29, 2018 USD ($) | Jun. 30, 2017 USD ($) | Jun. 29, 2018 USD ($) | Jun. 30, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Payment for pension benefits |  |  |  |  | $ 18,862 |
Settlement loss (gain) |  | $ 3,800 | $ 0 | $ 51 | 3,819 | $ 135
CH2M HILL Companies, Ltd. |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Defined benefit pension plan assets |  |  | 1,100,000 |  | 1,100,000 |
Defined benefit pension plan liabilities |  |  | $ 1,200,000 |  | $ 1,200,000 |
Number of noncontributory defined benefit pension plans |  |  | 3 |  | 3 |
Subsequent Event [Member] | CH2M HILL Companies, Ltd. |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |
Payment for pension benefits | $ 55,000 |  |  |  |  |

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- Definition Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees. + 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 (b) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit from irrevocable action relieving primary responsibility for benefit obligation and eliminating risk related to obligation and assets used to effect settlement. + 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 (h)(7) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of payment for pension benefits. Excludes other postretirement benefits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3536-108585 + Details
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