Segment Reporting (Details 1) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Entity-Wide Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries [Line Items]
Long Lived Assets, Total	$ 2,724,250	$ 2,790,317
ARGENTINA
Entity-Wide Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries [Line Items]
Long Lived Assets in Individual Foreign Countries	2,838	1,882
AUSTRALIA
Entity-Wide Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries [Line Items]
Long Lived Assets in Individual Foreign Countries	35,663	37,147
BOLIVIA
Entity-Wide Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries [Line Items]
Long Lived Assets in Individual Foreign Countries	230,301	234,306
MEXICO
Entity-Wide Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries [Line Items]
Long Lived Assets in Individual Foreign Countries	1,967,852	2,028,864
UNITED STATES
Entity-Wide Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries [Line Items]
Long Lived Assets in Entity's Country of Domicile	487,434	487,961
CHILE
Entity-Wide Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries [Line Items]
Long Lived Assets in Individual Foreign Countries	19	14
Other Countries [Member]
Entity-Wide Disclosure on Geographic Areas, Long-Lived Assets in Individual Foreign Countries [Line Items]
Long Lived Assets in Individual Foreign Countries	$ 143	$ 143