Employee Benefits - Summary of Remeasurements of Employee Benefit Plans (Detail) - Net benefit cost recognized in consolidated statements of accumulated other comprehensive income [member] - MXN ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of net defined benefit liability (asset) [line items]
Amount accumulated in other comprehensive income as of the beginning of the period, net of tax	$ 966	$ 810	$ 942
Actuarial losses arising from exchange rates	(2)	123	(12)
Remeasurements during the year, net of tax	295	288	(46)
Actuarial gains and (losses) arising from changes in financial assumptions	(367)	(255)	(74)
Amount accumulated in other comprehensive income as of the end of the period, net of tax	$ 892	$ 966	$ 810

Employee Benefits - Summary of Remeasurements of Employee Benefit Plans (Detail) - Net benefit cost recognized in consolidated statements of accumulated other comprehensive income [member] - MXN ($)
$ in Millions

12 Months Ended

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Disclosure of net defined benefit liability (asset) [line items]

Amount accumulated in other comprehensive income as of the beginning of the period, net of tax

$ 966

$ 810

$ 942

Actuarial losses arising from exchange rates

(2)

123