Annual report pursuant to Section 13 and 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
Jun. 30, 2016
Jun. 30, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative assets - future and forward contracts $ 38,763 $ 18,253
Derivative liabilities 36,454 17,897
Fair Value on a Recurring Basis    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Inventory 245,041 189,983
Total assets valued at fair value 278,773 201,347
Liability on borrowed metals 4,352 9,500
Product financing arrangement 59,358 39,425
Liability on margin accounts 8,182 6,908
Total liabilities, valued at fair value 100,164 66,822
Fair Value on a Recurring Basis | Level 1    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Inventory 245,041 189,983
Total assets valued at fair value 278,773 201,347
Liability on borrowed metals 4,352 9,500
Product financing arrangement 59,358 39,425
Liability on margin accounts 8,182 6,908
Total liabilities, valued at fair value 100,164 66,822
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 32,347 5,363
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 32,347 5,363
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 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 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 1,385 1,722
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 1,385 1,722
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 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 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   4,279
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   4,279
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
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
Forward contracts | Fair Value on a Recurring Basis    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Derivative liabilities 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 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  
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  
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 1,919 10,989
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 1,919 10,989
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