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INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE (Details) (MSC, USD $) In Thousands, unless otherwise specified	2 Months Ended	3 Months Ended		12 Months Ended		3 Months Ended		12 Months Ended	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Jan. 24, 2012	Dec. 31, 2012 Reported	Mar. 31, 2012 Reported	Dec. 31, 2012 Reported	Mar. 31, 2012 Adjustment	Dec. 31, 2012 Purchase price allocation adjustment	Mar. 31, 2012 Purchase price allocation adjustment
INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE
Interest acquired (as a percent)					49.00%
Interest held (as a percent)	49.00%	49.00%	49.00%
Fair value of investment in MSC from acquisition of Minera Andes				$ 262,883						$ 262,900	$ 225,000
Amortization of fair value increments	953	1,433	953	4,466			2,804		(1,851)
Net loss	$ 8,167	$ 2,440	$ (17,351)			$ 3,900	$ (19,202)	$ 1,900	$ 1,851

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Percentage of voting equity interests acquired in the business combination.

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