Financial risk management: Exchange rate risk (Details) - MXN ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financial risk management:
Asset	$ 57,515,881	$ 56,181,821
Liability	(18,744,704)	(19,500,432)
Exchange rate risk
Financial risk management:
Asset	164,370	45,003
Liability	(4,853)	(3,149)
Net assets at period closing	$ 159,517	$ 41,854

Expiry date 2020-01-01: The amount of resources: (a) controlled by the entity as a result of past events; and (b) from which future economic benefits are expected to flow to the entity. Effective 2020-01-01: The amount of a present economic resource controlled by the entity as a result of past events. Economic resource is a right that has the potential to produce economic benefits.

Expiry date 2020-01-01: The amount of present obligations of the entity arising from past events, the settlement of which is expected to result in an outflow from the entity of resources embodying economic benefits. Effective 2020-01-01: The amount of a present obligation of the entity to transfer an economic resource as a result of past events. Economic resource is a right that has the potential to produce economic benefits.

+ References + Details