Quarterly report pursuant to Section 13 or 15(d)

Assets and Liabilities, at Fair Value (Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details)

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Assets and Liabilities, at Fair Value (Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) - USD ($)
$ in Thousands
Sep. 30, 2016
Jun. 30, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets - future and forward contracts $ 35,878 $ 38,763
Derivative liabilities 13,519 36,454
Fair Value on a Recurring Basis    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Inventory 297,608 245,041
Total assets valued at fair value 326,383 278,773
Liability on borrowed metals 4,196 4,352
Product financing arrangement 117,789 59,358
Liability on margin accounts 8,372 8,182
Total liabilities, valued at fair value 135,504 100,164
Fair Value on a Recurring Basis | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Inventory 297,608 245,041
Total assets valued at fair value 326,383 278,773
Liability on borrowed metals 4,196 4,352
Product financing arrangement 117,789 59,358
Liability on margin accounts 8,372 8,182
Total liabilities, valued at fair value 135,504 100,164
Fair Value on a Recurring Basis | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Inventory 0 0
Total assets valued at fair value 0 0
Liability on borrowed metals 0 0
Product financing arrangement 0 0
Liability on margin accounts 0 0
Total liabilities, valued at fair value 0 0
Fair Value on a Recurring Basis | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Inventory 0 0
Total assets valued at fair value 0 0
Liability on borrowed metals 0 0
Product financing arrangement 0 0
Liability on margin accounts 0 0
Total liabilities, valued at fair value 0 0
Derivative Asset Open Purchases And Sales Commitments | Fair Value on a Recurring Basis    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets - future and forward contracts 21,874  
Derivative Asset Open Purchases And Sales Commitments | Fair Value on a Recurring Basis | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets - future and forward contracts 21,874  
Derivative Asset Open Purchases And Sales Commitments | Fair Value on a Recurring Basis | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets - future and forward contracts 0  
Derivative Asset Open Purchases And Sales Commitments | Fair Value on a Recurring Basis | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets - future and forward contracts 0  
Forward contracts | Fair Value on a Recurring Basis    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets - future and forward contracts   32,347
Forward contracts | Fair Value on a Recurring Basis | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets - future and forward contracts   32,347
Forward contracts | Fair Value on a Recurring Basis | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets - future and forward contracts   0
Forward contracts | Fair Value on a Recurring Basis | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets - future and forward contracts   0
Future contracts | Fair Value on a Recurring Basis    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets - future and forward contracts 6,901 1,385
Future contracts | Fair Value on a Recurring Basis | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets - future and forward contracts 6,901 1,385
Future contracts | Fair Value on a Recurring Basis | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets - future and forward contracts 0 0
Future contracts | Fair Value on a Recurring Basis | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets - future and forward contracts 0 0
Open sale and purchase commitments | Fair Value on a Recurring Basis    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative liabilities 662 1,919
Open sale and purchase commitments | Fair Value on a Recurring Basis | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative liabilities 662 1,919
Open sale and purchase commitments | Fair Value on a Recurring Basis | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative liabilities 0 0
Open sale and purchase commitments | Fair Value on a Recurring Basis | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative liabilities 0 0
Future contracts | Fair Value on a Recurring Basis    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative liabilities   13,914
Future contracts | Fair Value on a Recurring Basis | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative liabilities   13,914
Future contracts | Fair Value on a Recurring Basis | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative liabilities   0
Future contracts | Fair Value on a Recurring Basis | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative liabilities   0
Forward contracts | Fair Value on a Recurring Basis    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative liabilities 4,485 12,439
Forward contracts | Fair Value on a Recurring Basis | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative liabilities 4,485 12,439
Forward contracts | Fair Value on a Recurring Basis | Level 2    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative liabilities 0 0
Forward contracts | Fair Value on a Recurring Basis | Level 3    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative liabilities $ 0 $ 0