Segment Reporting (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Long Lived Assets
Long Lived Assets, Total	$ 2,675,811				$ 2,688,703				$ 2,675,811	$ 2,688,703	$ 2,790,317
Revenues
Total Revenue	205,929	230,593	254,406	204,564	246,911	343,575	231,090	199,624	895,492	1,021,200	515,457
United States [Member]
Long Lived Assets
Long Lived Assets in Entity's Country of Domicile	608,051				515,096				608,051	515,096	488,104
Revenues
Total Revenue									243,379	208,517	77,951
Australia [Member]
Long Lived Assets
Long Lived Assets in Individual Foreign Countries	29,408				33,999				29,408	33,999	37,147
Revenues
Total Revenue									18,848	18,737	10,618
Chile [Member]
Long Lived Assets
Long Lived Assets in Individual Foreign Countries	65				65				65	65	14
Argentina [Member]
Long Lived Assets
Long Lived Assets in Individual Foreign Countries	1,705				5,213				1,705	5,213	1,882
Revenues
Total Revenue									13,162	13,347	53,875
Bolivia [Member]
Long Lived Assets
Long Lived Assets in Individual Foreign Countries	240,905				230,956				240,905	230,956	234,306
Revenues
Total Revenue									178,005	267,502	142,988
Mexico [Member]
Long Lived Assets
Long Lived Assets in Individual Foreign Countries	1,795,677				1,903,374				1,795,677	1,903,374	2,028,864
Revenues
Total Revenue									$ 442,098	$ 513,097	$ 230,025