Income and Mining Taxes - Income (Loss) Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Tax Examination [Line Items]
Tax (expense) benefit	$ 3,717	$ (1,127)	$ 15,666	$ 9,751
Total	6,647	(11,122)	19,287	18,055
United States
Income Tax Examination [Line Items]
Income (loss) before tax, United States	(11,334)	(6,563)	(10,147)	14,090
Tax (expense) benefit	(2,309)	2,315	(1,792)	213
Argentina
Income Tax Examination [Line Items]
Tax (expense) benefit	(108)	945	(97)	2,070
Income (loss) before tax, Foreign	(180)	(129)	74	(457)
Canada
Income Tax Examination [Line Items]
Tax (expense) benefit	1,199	940	2,044	908
Income (loss) before tax, Foreign	(2,155)	6	(3,909)	8
Mexico
Income Tax Examination [Line Items]
Tax (expense) benefit	(2,499)	(4,766)	(15,821)	(14,689)
Income (loss) before tax, Foreign	20,542	(2,195)	33,669	6,455
Other jurisdictions
Income Tax Examination [Line Items]
Tax (expense) benefit	0	1,693	0	1,747
Income (loss) before tax, Foreign	$ (226)	$ (2,241)	$ (400)	$ (2,041)