Income Taxes Income Taxes (Details) $ in Millions, MXN in Billions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Aug. 31, 2016 USD ($)	Aug. 31, 2016 MXN
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Effective income tax rate, continuing operations	12.60%	41.00%
Timing and mix of pretax income with rates lower than US	(67.70%)	2.30%
Impact of foreign exchange	28.00%	(9.10%)
Other reconciling items	17.30%	12.80%
Mexican Tax Authority | Tax Year 2010
Income Tax Contingency [Line Items]
Number of subsidiaries in a tax assessment			1	1
Tax assessment			$ 157	MXN 3