Other, Net (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Other Income and Expenses [Abstract]
Foreign exchange gain (loss)	$ (3,309)	$ 786	$ (3,979)	$ 1,992
Gain (loss) on sale of assets and investments	586	513	345	(1,552)
Gain on sale of the Joaquin project	0	0	0	21,138
Gain on repurchase of the Rochester royalty obligation	0	2,332	0	2,332
Mexico Inflation Adjustment	1,939	0	1,939	0
Other	1,328	343	2,752	863
Other, net	$ 544	$ 3,974	$ 1,057	$ 24,773