Income Taxes (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended		12 Months Ended				12 Months Ended		12 Months Ended			0 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Internal Revenue Service (IRS) [Member]	Dec. 31, 2011 Internal Revenue Service (IRS) [Member]	Dec. 31, 2012 Internal Revenue Service (IRS) [Member] Track Maintenance Credits [Member]	Dec. 31, 2012 Internal Revenue Service (IRS) [Member] Alternative Minimum Tax Credits [Member]	Dec. 31, 2012 Internal Revenue Service (IRS) [Member] Maximum [Member]	Dec. 31, 2012 State and Local Jurisdiction [Member]	Dec. 31, 2012 State and Local Jurisdiction [Member] Minimum [Member]	Dec. 31, 2012 State and Local Jurisdiction [Member] Maximum [Member]	Dec. 31, 2012 Mexico Federal Tax [Member]	Dec. 17, 2012 Mexico Federal Tax [Member] Years 2012 and 2013 [Member]	Dec. 17, 2012 Mexico Federal Tax [Member] Year 2014 [Member]	Dec. 17, 2012 Mexico Federal Tax [Member] Year 2015 [Member]
Income Tax Contingency [Line Items]
Amount the Company's book basis exceeded the tax basis of its foreign investments	$ 1,187.3
Potential income taxes on foreign investments	415.5
Statutory income tax rate			35.00%									30.00%	29.00%	28.00%
Net operating loss carryforward, period							20 years		5 years	20 years
Net operating loss carryforward, amount			10.7					391.4			117.5
Federal operating loss carryforward not recognized in the financial statements				73.5
Tax credit carryforward, amount			29.4		22.6	1.5					6.8
Valuation allowance for deferred tax assets	4.3	15.5
Change in valuation allowance, amount	$ (11.2)