Acquisitions (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		9 Months Ended
	Apr. 17, 2015	Feb. 20, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Business Acquisition [Line Items]
Revenue			$ 162,552	$ 170,938	$ 481,770	$ 495,133
Common stock issued for the acquisition of Paramount Gold and Silver Corp.					32,667,327
Stock Issued During Period, Value, Acquisitions (in dollars per share)					$ 5.78
Assets acquired:
Receivables			121,106		$ 121,106		$ 138,607
Ore on leach pads			68,695		68,695		48,204
Property, Plant and Equipment, Net			261,043		261,043		227,911
Mining properties, net			851,590		851,590		$ 501,192
Business Acquisition, Pro Forma Information [Abstract]
Net income (loss)			(14,219)	3,466	(64,185)	(76,846)
Paramount Gold and Silver Corp. [Member]
Business Acquisition [Line Items]
Common shares issued	$ 188,817
Cash	8,530
Transaction advisory fees and other acquisition costs	4,020
Total purchase price	201,367
Assets acquired:
Cash and cash equivalents	118
Other current assets	1,685
Property, plant, and equipment, net	215
Mining properties, net	305,175
Assets	307,193
Liabilities:
Accounts payable and accrued liabilities	2,737
Deferred income taxes	103,089
Liabilities	105,826
Net assets acquired	$ 201,367
Wharf Gold Mine [Member]
Business Acquisition [Line Items]
Cash		$ 99,800
Transaction advisory fees and other acquisition costs			2,100		2,100
Assets acquired:
Other current assets		2,924
Cash		982
Receivables		3,061
Inventory		2,147
Ore on leach pads		12,710
Property, Plant and Equipment, Net		30,055
Mining properties, net		81,189
Other non-current assets		3,966
Assets		137,034
Liabilities:
Accounts payable and accrued liabilities		5,494
Deferred income taxes		9,680
Reclamation		18,270
Other non-current liabilities		3,750
Liabilities		37,194
Net assets acquired		$ 99,840
Business Acquisition, Pro Forma Information [Abstract]
Revenue				190,323	499,770	555,344
Income (loss) before income and mining taxes			(22,479)	(9,125)	(72,688)	(79,190)
Net income (loss)			$ (14,219)
Net income (loss)				$ 7,383	$ (64,237)	$ (60,554)