DISCLOSURES ABOUT THE FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - USD ($)	Dec. 28, 2019	Dec. 29, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets recorded for the investments held	$ 36,290,000	$ 37,516,000
Liabilities recorded for the investments held	36,290	37,516
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	36,500,000	40,024,000
Derivative financial instruments, net	0	0
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	0	0
Derivative financial instruments, net	3,247,000	9,147,000
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities	0	0
Derivative financial instruments, net	0	0
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	765,704,000	742,601,000
Trading securities	36,500,000	40,024,000
Derivative financial instruments, net	3,247,000	9,147,000
Estimated Fair value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt	826,413,000	683,602,000
EMD
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value of remaining ownership	210,000	2,508,000
Valmont Deferred Compensation Plan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets recorded for the investments held	36,290,000	37,516,000
Liabilities recorded for the investments held	$ 36,290	$ 37,516