CHANGES IN BUSINESS - Additional Information (Details) t in Millions, $ in Millions	Dec. 29, 2017 USD ($) fabrication_facility t
Business Acquisition [Line Items]
Annual melt capacity	7.2
U.S. Rebar Steel Mill and Fabrication Assets
Business Acquisition [Line Items]
Cash purchase price of acquisition \| $	$ 600.0
Number of rebar fabrication facilities acquired \| fabrication_facility	33
Annual melt capacity	2.7

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3213-108585

Name:	us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration