GOODWILL AND INTANGIBLE ASSETS - Carrying Values of Trade Names - (Details) - USD ($) $ in Thousands	Jun. 25, 2016	Dec. 26, 2015
Webforge
Non-amortized intangible assets
Carrying value of trade names	$ 9,545	$ 10,430
Valmont SM
Non-amortized intangible assets
Carrying value of trade names	9,246	8,919
Newmark
Non-amortized intangible assets
Carrying value of trade names	11,111	11,111
Ingal EPS/Ingal Civil Products
Non-amortized intangible assets
Carrying value of trade names	7,781	8,504
Donhad
Non-amortized intangible assets
Carrying value of trade names	5,870	6,415
Shakespeare
Non-amortized intangible assets
Carrying value of trade names	4,000	4,000
Industrial Galvanizers
Non-amortized intangible assets
Carrying value of trade names	2,436	2,662
Other
Non-amortized intangible assets
Carrying value of trade names	14,107	13,889
Trade Names
Non-amortized intangible assets
Carrying value of trade names	$ 64,096	$ 65,930