Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013
Internal Revenue Service (IRS) [Member]
Income Tax Examination [Line Items]
Tax years under examination	2008 and 2009
Mexican Tax Authorities [Member]
Income Tax Examination [Line Items]
Tax years under examination	2000 to 2005 and 2007
Tax assessments relating to Mexican tax examinations for the years 2000 to 2005 and 2007	219,940
Bonds provided to the Mexican government related to the 2000 to 2004 assessments	188,060