INVESTMENT IN MINERA SANTA CRUZ S.A. ("MSC") - SAN JOSE MINE (Details 3) (USD $) In Thousands, unless otherwise specified	2 Months Ended	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Summary of MSC's financial information from operations
(Loss) income on investment in MSC, net of amortization		$ (237)	$ 3,049
Current assets		66,680		91,918
Total assets		1,124,963		1,150,937
Current liabilities		13,917		25,195
Total liabilities		242,576		261,346
MSC
Summary of MSC's financial information from operations
Sales percentage	100.00%	100.00%
Sales	40,228	43,813
Net income percentage	100.00%	100.00%
Net income	8,167	2,440	(17,351)
Ownership interest (as a percent)	49.00%	49.00%	49.00%
Net income on investment in MSC	4,002	1,196		25,301
Amortization of fair value increments	(953)	(1,433)	(953)	(4,466)
(Loss) income on investment in MSC, net of amortization	3,049	(237)
Current assets		124,500
Total assets		791,400
Current liabilities		64,000
Total liabilities		$ 247,600