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GOODWILL AND OTHER INTANGIBLE ASSETS - Carrying Value of Goodwill by Reporting Unit (Details) - USD ($) $ in Thousands	12 Months Ended
	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

X

- 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
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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

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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
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