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SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details) $ in Thousands	12 Months Ended
	Aug. 31, 2018 USD ($) levels	Aug. 31, 2017 USD ($)	Aug. 31, 2016 USD ($)	Sep. 01, 2018 USD ($)
Retainage included in accounts receivable	$ 41,800	$ 43,200
Goodwill impairment	515	1,982
Goodwill	64,310	64,915	$ 66,373
Transaction gains (losses)	$ 1,800	2,000	$ (15,600)
Number of fair value hierarchy | levels	3
One reporting unit within Americas Fabrication
Goodwill	$ 51,100	$ 51,600
Receivables secured by credit insurance or letters of credit
Percentage of accounts receivable secured by credit insurance or letters of credit	18.00%	28.00%
Certain fabrication projects
Sales recognized in excess of amounts billed	$ 49,200	$ 23,100
Forecast | Accounting Standards Update 2014-09
Cumulative effect of new accounting principle on retained earnings				$ 2,700

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