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The amount of cash balances held at banks.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 7
-IssueDate 2018-01-01
-Paragraph 45
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2018-03-01&anchor=para_45&doctype=Standard
-URIDate 2018-03-16

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The amount of cash on hand and demand deposits, along with short-term, highly liquid investments that are readily convertible to known amounts of cash and that are subject to an insignificant risk of changes in value. [Refer: Cash; Cash equivalents]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 7
-IssueDate 2018-01-01
-Paragraph 45
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=7&date=2018-03-01&anchor=para_45&doctype=Standard
-URIDate 2018-03-16

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 12
-IssueDate 2018-01-01
-Paragraph B13
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IFRS&num=12&date=2018-03-01&anchor=para_B13_a&doctype=Appendix&seq=2
-URIDate 2018-03-16

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 54
-Subparagraph i
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_54_i&doctype=Standard
-URIDate 2018-03-16

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The amount of cash and cash equivalents whose use or withdrawal is restricted. [Refer: Cash and cash equivalents]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2018-01-01
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2018-03-01&anchor=para_55&doctype=Standard
-URIDate 2018-03-16

Name:	ifrs-full_RestrictedCashAndCashEquivalents
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Data Type:	xbrli:monetaryItemType
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A classification of cash equivalents representing short-term deposits. [Refer: Cash equivalents]

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A classification of cash equivalents representing short-term investments. [Refer: Cash equivalents]

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Cash Deposit, Mandatory Convertible Bonds

No definition available.

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Namespace Prefix:	mt_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Cash Deposit, Various Environmental Obligations and True Sales of Receivable Programs

No definition available.