Derivative Instruments (Narrative) (Details) (Foreign Currency Forward Contracts [Member], Not Designated as Hedging Instrument [Member]) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2014 USD ($)	Mar. 31, 2014 MXN	Jun. 30, 2013 USD ($)	Jun. 30, 2013 MXN
Derivative [Line Items]
Aggregate notional amount of foreign currency forward contracts	$ 345.0	4,642.5	$ 325.0	4,202.3
Maturity date of foreign currency forward contracts	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2013
Weighted-average exchange rate of foreign currency forward contracts (in Ps per USD)		13.46		12.93