GOODWILL AND INTANGIBLE ASSETS - Impairment (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 24, 2016	Dec. 26, 2015	Sep. 24, 2016
Indefinite-lived Intangible Assets [Line Items]
Goodwill	$ 327,863,000	$ 336,916,000	$ 327,863,000
ESS
Indefinite-lived Intangible Assets [Line Items]
Goodwill	96,716,000	101,275,000	96,716,000
ESS | Webforge
Indefinite-lived Intangible Assets [Line Items]
Impairment	5,000,000	830,000
Energy & Mining
Indefinite-lived Intangible Assets [Line Items]
Goodwill	76,191,000	81,159,000	76,191,000
Coatings Segment
Indefinite-lived Intangible Assets [Line Items]
Goodwill	59,882,000	$ 59,719,000	59,882,000
Coatings Segment | Industrial Galvanizers
Indefinite-lived Intangible Assets [Line Items]
Impairment			1,100,000
Offshore Structures | Energy & Mining
Indefinite-lived Intangible Assets [Line Items]
Goodwill	$ 13,872		$ 13,872