Segment Reporting (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Long Lived Assets
Long Lived Assets, Total	$ 2,638,789		$ 2,638,789		$ 2,688,704
Revenues
Total Revenue	254,406	231,090	458,970	430,714
UNITED STATES
Long Lived Assets
Long Lived Assets in Entity's Country of Domicile	522,057		522,057		515,096
Revenues
Total Revenue	55,277	40,446	84,411	102,818
AUSTRALIA
Long Lived Assets
Long Lived Assets in Individual Foreign Countries	30,763		30,763		33,999
Revenues
Total Revenue	5,232	6,550	11,946	9,630
CHILE
Long Lived Assets
Long Lived Assets in Individual Foreign Countries	65		65		65
ARGENTINA
Long Lived Assets
Long Lived Assets in Individual Foreign Countries	1,775		1,775		5,213
Revenues
Total Revenue	4,149	4,769	7,767	4,455
BOLIVIA
Long Lived Assets
Long Lived Assets in Individual Foreign Countries	240,879		240,879		230,956
Revenues
Total Revenue	53,383	55,598	94,759	101,919
MEXICO
Long Lived Assets
Long Lived Assets in Individual Foreign Countries	1,843,250		1,843,250		1,903,375
Revenues
Total Revenue	$ 136,365	$ 123,727	$ 260,087	$ 211,892