Employee benefits - Analysis of net period cost (Details) - MXN ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee benefits
Current service cost	$ 3,657	$ 2,421	$ 2,012
Interest cost on benefit obligation	1,000	701	537
Net period cost	$ 4,657	$ 3,122	$ 2,549

The amount of post-employment benefit expense relating to defined benefit plans. [Refer: Defined benefit plans [member]]

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name IAS
-Number 19
-IssueDate 2017-01-01
-Paragraph 5
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=19&date=2017-03-01&anchor=para_5&doctype=Standard
-URIDate 2017-03-09

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