Weighted average amortization period of finite-lived intangible assets acquired either individually or as part of a group of assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The amount of goodwill arising from a business combination that is expected to be deductible for tax purposes.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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ACQUISITIONS - Narrative (Details) - USD ($) $ in Thousands						1 Months Ended			3 Months Ended		6 Months Ended
ACQUISITIONS - Narrative (Details) - USD ($) $ in Thousands	May 13, 2019	Feb. 11, 2019	Dec. 31, 2018	Oct. 18, 2018	Aug. 03, 2018	Apr. 30, 2019	Jan. 31, 2019	Mar. 30, 2018	Sep. 28, 2019	Sep. 29, 2018	Jun. 29, 2019	Dec. 29, 2018	Mar. 31, 2018
Business Acquisition [Line Items]
Goodwill									$ 421,679			$ 385,207
Connect-It Wireless, Inc.
Business Acquisition [Line Items]
Cash paid in acquisition	$ 6,034
Goodwill	3,299
United Galvanizing
Business Acquisition [Line Items]
Cash paid in acquisition		$ 26,000
Goodwill		11,715
Consideration transfered		28,000
Contingent consideration liability, current		2,000
Property, plant, and equipment acquired		11,016
Larson Camouflage
Business Acquisition [Line Items]
Cash paid in acquisition			$ 31,106
Goodwill			14,519
Consideration transfered			34,562
Property, plant, and equipment acquired			$ 1,151
Contingent consideration liability, as percent of purchase price (percent)			10.00%
CSP Coatings Systems Of Auckland
Business Acquisition [Line Items]
Cash paid in acquisition				$ 17,711
Goodwill				5,120
Property, plant, and equipment acquired				7,373
Walpar
Business Acquisition [Line Items]
Goodwill					$ 45,453
Consideration transfered					$ 57,805		$ 23,082
Percentage acquired					72.00%		28.00%
Convert Italia S.p.A
Business Acquisition [Line Items]
Goodwill					$ 42,169
Goodwill expected to be tax deductible					0
Consideration transfered					$ 43,504						$ 18,700
Percentage acquired					75.00%
Walpart, Convert, and Torrent
Business Acquisition [Line Items]
Revenue of acquiree since acquisition									$ 26,999	$ 94,975
Valmont SM
Business Acquisition [Line Items]
Consideration transfered						$ 4,763
Percentage acquired						4.80%
Valmont Industria e Commercio Ltda.
Business Acquisition [Line Items]
Consideration transfered								$ 5,510
Percentage acquired													10.00%
Customer Relationships \| Connect-It Wireless, Inc.
Business Acquisition [Line Items]
Customer relationships and other intangible assets	$ 828
Customer Relationships \| United Galvanizing
Business Acquisition [Line Items]
Customer relationships and other intangible assets		$ 4,034
Useful life		10 years
Customer Relationships \| Larson Camouflage
Business Acquisition [Line Items]
Customer relationships and other intangible assets			$ 17,050
Useful life			12 years
Customer Relationships \| CSP Coatings Systems Of Auckland
Business Acquisition [Line Items]
Customer relationships and other intangible assets				$ 3,113
Useful life				10 years
Customer Relationships \| Walpar
Business Acquisition [Line Items]
Useful life					12 years
Reduction in customer relationships							$ 3,500
Patents & Proprietary Technology \| Convert Italia S.p.A
Business Acquisition [Line Items]
Useful life					15 years
Trade Names \| United Galvanizing
Business Acquisition [Line Items]
Customer relationships and other intangible assets		$ 894