PERSONNEL EXPENSES AND DEFERRED EMPLOYEE BENEFITS - Key Management Personnel's Compensation (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Employee Benefits [Abstract]
Base salary and directors fees	$ 10	$ 7	$ 8
Short-term performance-related bonus	12	3	9
Post-employment benefits	2	1	1
Share-based payments	$ 7	$ 4	$ 0

The amount of compensation to key management personnel in the form of post-employment benefits. [Refer: Key management personnel of entity or parent [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 24
-IssueDate 2021-01-01
-Paragraph 17
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=24&code=ifrs-tx-2021-en-r&anchor=para_17_b&doctype=Standard
-URIDate 2021-03-24

+ Details

Name:	ifrs-full_KeyManagementPersonnelCompensationPostemploymentBenefits
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of compensation to key management personnel in the form of share-based payments. [Refer: Key management personnel of entity or parent [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 24
-IssueDate 2021-01-01
-Paragraph 17
-Subparagraph e
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=24&code=ifrs-tx-2021-en-r&anchor=para_17_e&doctype=Standard
-URIDate 2021-03-24

+ Details

Name:	ifrs-full_KeyManagementPersonnelCompensationSharebasedPayment
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of compensation to key management personnel in the form of short-term employee benefits. [Refer: Key management personnel of entity or parent [member]]

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 24
-IssueDate 2021-01-01
-Paragraph 17
-Subparagraph a
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=24&code=ifrs-tx-2021-en-r&anchor=para_17_a&doctype=Standard
-URIDate 2021-03-24

+ Details

Name:	ifrs-full_KeyManagementPersonnelCompensationShorttermEmployeeBenefits
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Employee Benefits [Abstract]

+ References

No definition available.

+ Details

Name:	mt_EmployeeBenefitsAbstract
Namespace Prefix:	mt_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Key Management Personnel Compensation, Base Salary And Directors Fees

+ References

No definition available.

+ Details

Name:	mt_KeyManagementPersonnelCompensationBaseSalaryAndDirectorsFees
Namespace Prefix:	mt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration