Income and Mining Taxes - Income (Loss) Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Tax Examination [Line Items]
Tax (expense) benefit	$ (5,546)	$ 3,717	$ (14,204)	$ 15,666
Total	(42,310)	6,647	(75,862)	19,287
United States
Income Tax Examination [Line Items]
United States, Income (loss) before tax	(16,835)	(11,334)	(22,882)	(10,147)
Tax (expense) benefit	(1,399)	(2,309)	(3,561)	(1,792)
Canada
Income Tax Examination [Line Items]
Tax (expense) benefit	7,547	1,199	17,339	2,044
Foreign, Income (loss) before tax	(27,568)	(2,155)	(54,093)	(3,909)
Mexico
Income Tax Examination [Line Items]
Tax (expense) benefit	(600)	(2,499)	424	(15,821)
Foreign, Income (loss) before tax	2,292	20,542	1,521	33,669
Other jurisdictions
Income Tax Examination [Line Items]
Tax (expense) benefit	(2)	(108)	2	(97)
Foreign, Income (loss) before tax	$ (199)	$ (406)	$ (408)	$ (326)