Income Taxes (Details) $ in Millions, $ in Billions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Aug. 31, 2016 USD ($)	Aug. 31, 2016 MXN ($)
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Effective income tax rate, continuing operations	79.60%	12.60%
Timing and mix of pretax income with rates differing from US	33.60%	(67.70%)
Impact of foreign exchange	1.90%	28.00%
Other reconciling items	23.10%	17.30%
Mexican Tax Authority | Tax Year 2010
Income Tax Contingency [Line Items]
Number of subsidiaries in a tax assessment			1	1
Tax assessment			$ 157	$ 3