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Schedule of actuarial assumptions used for calculating postemployment healthcare benefits (Details) - Number | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020
IfrsStatementLineItems [Line Items] |  |
General mortality table | Millennium Plan: AT-2012 segregated by gender Plan 35%: AT-2000 Male aggravated by 15% Supplementation: AT-2000 aggravated by 10% segregated by gender | Millennium Plan: AT-2012 segregated by gender Plan 35%: AT-2000 Male aggravated by 15% Supplementation: AT-2000 aggravated by 10% segregated by gender
Actuarial assumption of expected rates of inflation | 5.03% | 3.32%
Post Employment Healthcare Benefits [Member] |  |
IfrsStatementLineItems [Line Items] |  |
General mortality table | AT 2000 segregated by gender 20% | AT 2000 segregated by gender 20%
Actuarial assumption of discount rates | 10.55% | 6.53%
Actuarial assumption of expected rates of inflation | 5.03% | 3.32%
Real increase in medical costs based on age (Aging Factor) | 0.5% - 3.00% real p.a. | 0.5% - 3.00% real p.a.
Actuarial assumption of medical cost trend rates | 4.10% | 4.10%
Average medical cost | 1,011.42 | 913.00

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- Definition The discount rate used as the significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit obligation, at present value; Actuarial assumptions [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2021-01-01 -Paragraph 144 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2021-en-r&anchor=para_144&doctype=Standard -URIDate 2021-03-24 + Details
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Period Type: | instant

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- Definition The expected rate of inflation that is used as a significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit plans [member]; Defined benefit obligation, at present value; Actuarial assumptions [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2021-01-01 -Paragraph 144 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2021-en-r&anchor=para_144&doctype=Standard -URIDate 2021-03-24 + Details
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- Definition Medical cost trend rate used as significant actuarial assumption to determine the present value of a defined benefit obligation. [Refer: Defined benefit obligation, at present value; Actuarial assumptions [member]] + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Name IAS -Number 19 -IssueDate 2021-01-01 -Paragraph 144 -URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2021-en-r&anchor=para_144&doctype=Standard -URIDate 2021-03-24 + Details
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Balance Type: | na
Period Type: | instant

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- References No definition available. + Details
Name: | sid_AverageMedicalCost
Namespace Prefix: | sid_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

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- Definition Represents the information about general mortality table. + References No definition available. + Details
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- References No definition available. + Details
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- References No definition available. + Details
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Namespace Prefix: | sid_
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- Details
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Namespace Prefix: |
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Period Type: |