XML 160 R137.htm IDEA: XBRL DOCUMENT v3.21.1

EMPLOYEE BENEFITS - Defined benefit pension plan - Assumptions used to calculate defined benefit plans (Details) - Defined benefit pension plan	Dec. 31, 2020	Dec. 31, 2019
Brazil
Summary of assumptions used to calculate the defined benefit plans
Average discount rate	6.56%	7.16%
North America
Summary of assumptions used to calculate the defined benefit plans
Rate of increase in compensation	3.00%	3.00%
North America | Minimum
Summary of assumptions used to calculate the defined benefit plans
Average discount rate	2.25%	3.00%
North America | Maximum
Summary of assumptions used to calculate the defined benefit plans
Average discount rate	2.50%	3.25%

X

- References

No definition available.

+ Details

Name:	ggb_SummaryOfAssumptionsUsedToCalculateDefinedBenefitPlansAbstract
Namespace Prefix:	ggb_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- 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 2020-01-01
-Paragraph 144
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2020-en-r&anchor=para_144&doctype=Standard
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_ActuarialAssumptionOfDiscountRates
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

The expected rate of salary increases 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 2020-01-01
-Paragraph 144
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IAS&num=19&code=ifrs-tx-2020-en-r&anchor=para_144&doctype=Standard
-URIDate 2020-01-01

+ Details

Name:	ifrs-full_ActuarialAssumptionOfExpectedRatesOfSalaryIncreases
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Details

Name:	ifrs-full_DefinedBenefitPlansAxis=ifrs-full_DefinedBenefitPlansOtherThanMultiemployerPlansStatePlansAndPlansThatShareRisksBetweenEntitiesUnderCommonControlMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_StatementGeographicalAxis=country_BR
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	srt_StatementGeographicalAxis=srt_NorthAmericaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_BottomOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	ifrs-full_RangeAxis=ifrs-full_TopOfRangeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: