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GOODWILL AND OTHER INTANGIBLE ASSETS - Carrying Value of Goodwill by Reporting Unit (Details) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 27, 2019 | Dec. 28, 2018
Changes in carrying value of goodwill |  |
Goodwill at beginning of period | $ 97,748 | $ 38,184
Additional Purchase Cost | 39,690 | 59,466
Additions/Adjustments | (9,791) | 98
Goodwill at end of period | 127,647 | 97,748
Energy |  |
Changes in carrying value of goodwill |  |
Goodwill at beginning of period | 96,999 | 37,435
Additional Purchase Cost | 39,690 | 59,466
Additions/Adjustments | (9,791) | 98
Goodwill at end of period | 126,898 | 96,999
Engineering and Consulting |  |
Changes in carrying value of goodwill |  |
Goodwill at beginning of period | 749 | 749
Goodwill at end of period | $ 749 | $ 749

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- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266 + Details
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- Definition Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267 + Details
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- Definition Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 16 -URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e961-128460 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=108376223&loc=d3e13816-109267 + Details
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