Risk and Capital Management - Summary of Risk Level of Financial Assets (Parenthetical) (Detail) - BRL (R$) R$ in Millions	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2017
Disclosure of risk level of financial assets [Line Items]
Derivatives assets	R$ 23,466	R$ 22,843	R$ 24,231
Insurance financial assets [member]
Disclosure of risk level of financial assets [Line Items]
Derivatives assets	R$ 449	R$ 194

The amount of financial assets classified as derivative instruments. [Refer: Financial assets; Derivatives [member]]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 1
-IssueDate 2017-01-01
-Paragraph 55
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=1&date=2017-03-01&anchor=para_55&doctype=Standard
-URIDate 2017-03-09

Name:	ifrs-full_DerivativeFinancialAssets
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant