Income and Mining Taxes - Income (Loss) Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Examination [Line Items]
Tax (expense) benefit	$ 3,785	$ 14,289	$ 19,451	$ 24,040
Total	(49,259)	2,561	(29,972)	20,616
United States
Income Tax Examination [Line Items]
Income (loss) before tax, United States	(35,250)	(6,055)	(45,397)	8,036
Tax (expense) benefit	(908)	(2,892)	(2,700)	(4,072)
Argentina
Income Tax Examination [Line Items]
Tax (expense) benefit	(75)	(366)	(172)	1,704
Income (loss) before tax, Foreign	(2,058)	738	(1,985)	281
Canada
Income Tax Examination [Line Items]
Tax (expense) benefit	4,432	0	6,476	0
Income (loss) before tax, Foreign	(13,194)	0	(17,103)	0
Mexico
Income Tax Examination [Line Items]
Tax (expense) benefit	(7,234)	(9,057)	(23,055)	(23,745)
Income (loss) before tax, Foreign	1,419	3,210	35,088	9,665
Other jurisdictions
Income Tax Examination [Line Items]
Tax (expense) benefit	0	(1,974)	0	2,073
Income (loss) before tax, Foreign	$ (176)	$ 4,668	$ (575)	$ 2,634