Contingencies - Additional Information (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended			12 Months Ended
	Apr. 30, 2016	Oct. 31, 2011	Jun. 30, 2016	Jun. 30, 2015	Sep. 30, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2005
Loss Contingencies [Line Items]
Other current liabilities						$ 13,083	$ 23,228
Other liabilities						9,235	12,354
New Almaden Mine (Formerly Referred to as Guadelupe River Watershed) [Member] | Natural Resource Damage Claim [Member]
Loss Contingencies [Line Items]
Expense recognized						1,200		$ 800
Total reserve						1,500
Other current liabilities						200
Other liabilities						1,300
Accrued balance						500
Original estimated project costs	$ 1,600
Revised estimated project costs, Low Estimate	3,300
Revised estimated project costs, High Estimate	$ 4,400
Lawn and Garden Indemnification Claim [Member]
Loss Contingencies [Line Items]
Indemnification claims						10,000
Escrow deposit						$ 8,600
Escrow deposit due to be settled date						2016-08
Pending Litigation [Member] | New Idria Mercury Mine [Member] | EPA Notice Letter [Member]
Loss Contingencies [Line Items]
Expense recognized		$ 1,900	$ 1,000
Loss contingency costs						$ 1,600
Accrued balance							1,300
Total reserve						2,500	$ 2,000
Other current liabilities						300
Other liabilities						2,200
Settled Litigation [Member] | Patent Infringement Against Orbis Corp [Member] | Loss From Patent Infringement [Member]
Loss Contingencies [Line Items]
Accrued balance					$ 3,000
Litigation settlement, amount						200
Contingency accrual reversal				$ 3,000
Settled Litigation [Member] | Patent Infringement Against Orbis Corp [Member] | Loss From Patent Infringement [Member] | Maximum [Member]
Loss Contingencies [Line Items]
Litigation settlement, amount						$ 3,100