Income and Mining Taxes (Details 7) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Regular net operating losses	$ 439,138
Alternative minimum tax net operating losses	117,362
Capital losses	91,019
Alternative minimum tax credits	4,142
Foreign tax credits	52,181
United States [Member]
Operating Loss Carryforwards [Line Items]
Regular net operating losses	245,683
Alternative minimum tax net operating losses	117,362
Capital losses	91,019
Alternative minimum tax credits	4,142
Foreign tax credits	52,181
Argentina [Member]
Operating Loss Carryforwards [Line Items]
Regular net operating losses	16,588
Alternative minimum tax net operating losses	0
Capital losses	0
Alternative minimum tax credits	0
Foreign tax credits	0
Canada [Member]
Operating Loss Carryforwards [Line Items]
Regular net operating losses	1,633
Alternative minimum tax net operating losses	0
Capital losses	0
Alternative minimum tax credits	0
Foreign tax credits	0
Mexico [Member]
Operating Loss Carryforwards [Line Items]
Regular net operating losses	49,747
Alternative minimum tax net operating losses	0
Capital losses	0
Alternative minimum tax credits	0
Foreign tax credits	0
New Zealand [Members]
Operating Loss Carryforwards [Line Items]
Regular net operating losses	102,535
Alternative minimum tax net operating losses	0
Capital losses	0
Alternative minimum tax credits	0
Foreign tax credits	0
Other [Member]
Operating Loss Carryforwards [Line Items]
Regular net operating losses	22,952
Alternative minimum tax net operating losses	0
Capital losses	0
Alternative minimum tax credits	0
Foreign tax credits	$ 0