SHORT-TERM DEBT AND LONG-TERM DEBT - Credit Lines (Details) R$ in Thousands, $ in Millions	Dec. 31, 2025 BRL (R$)	Sep. 30, 2022 USD ($)
Global Credit Line
SHORT-TERM DEBT AND LONG-TERM DEBT
Maximum borrowing capacity	R$ 4,815	$ 875

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

No definition available.

Name:	ggb_IfrsLineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	ggb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant