SEGMENT AND GEOGRAPHIC INFORMATION - Sales by Type of Products (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018
Disclosure of products and services [line items]
Sales	$ 38,467	$ 39,184
Flat products
Disclosure of products and services [line items]
Sales	24,062	24,136
Long products
Disclosure of products and services [line items]
Sales	7,384	8,160
Tubular products
Disclosure of products and services [line items]
Sales	1,189	1,104
Mining products
Disclosure of products and services [line items]
Sales	662	525
Others
Disclosure of products and services [line items]
Sales	$ 5,170	$ 5,259

The amount of revenue from contracts with customers. A customer is a party that has contracted with an entity to obtain goods or services that are an output of the entity’s ordinary activities in exchange for consideration. [Refer: Revenue]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 15
-IssueDate 2018-01-01
-Paragraph 113
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=15&date=2018-03-01&anchor=para_113_a&doctype=Standard
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 15
-IssueDate 2018-01-01
-Paragraph 114
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=15&date=2018-03-01&anchor=para_114&doctype=Standard
-URIDate 2018-03-16

Name:	ifrs-full_RevenueFromContractsWithCustomers
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration