Income and Mining Taxes - Reconciliation of Effective Income Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income and mining tax (expense) benefit at statutory rate	$ (75,185)	$ (14,052)	$ 14,037
State tax provision from continuing operations	(1,243)	(2,284)	(26)
Change in valuation allowance	77,220	(2,471)	(86,712)
Effect of tax legislation	0	0	88,174
Percentage depletion	(820)	(89)	(703)
Uncertain tax positions	(2,358)	(1,830)	(2,596)
U.S. and foreign permanent differences	(2,272)	(3,314)	(2,348)
Foreign exchange rates	7,066	3,973	14,180
Foreign inflation and indexing	2,933	2,374	2,346
Foreign tax rate differences	(19,729)	24	(2,929)
Mining, foreign withholding, and other taxes	2,746	3,857	11,274
Other, net	513	(2,968)	(5,699)
Income and mining tax benefit (expense)	$ (11,129)	$ (16,780)	$ 28,998