Related Party transactions - Summary of Total Costs of Key Management Personnel (Detail) - BRL (R$) R$ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of key management personnel compensation [abstract]
Remuneration	R$ 32	R$ 25	R$ 19
Profit sharing (reversal)	1	(1)	2
Assistance benefits	2	2	1
Total	R$ 35	R$ 26	R$ 22

The amount of compensation to key management personnel. [Refer: Key management personnel of entity or parent [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 24
-IssueDate 2017-01-01
-Paragraph 17
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=24&date=2017-03-01&anchor=para_17&doctype=Standard
-URIDate 2017-03-09

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