Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies Commitment and Contingencies (Details)

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Commitments and Contingencies Commitment and Contingencies (Details)
Aug. 31, 2016
ounce
Asahi Refining USA, Inc  
Long-term Purchase Commitment [Line Items]  
Operating leases, term of contract (in years) 1 year
Operating leases, renewal term (in years) 1 year
Lease fees, subject to adjustment (in months) 6 months
Supply Commitment | Asahi Refining USA, Inc  
Long-term Purchase Commitment [Line Items]  
Supply commitment, term (in years) 3 years
Supply commitment, renewal term (in years) 2 years
Price subject to adjustment, period (in months) 6 months
Silver Products | AM&ST Associates, LLC  
Long-term Purchase Commitment [Line Items]  
Purchase commitment, period (in years) 3 years
Purchase commitment, renewal term (in years) 2 years
Minimum quantity required 300,000
Price subject to adjustment, period (in months) 6 months
Guarantor Subsidiaries [Member] | Asahi Refining USA, Inc  
Long-term Purchase Commitment [Line Items]  
Agreement to lease 100,000