Quarterly report pursuant to Section 13 or 15(d)

Derivative Instrument and Hedging Transactions (Hedging of Precious Metals Inventory) (Details)

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Derivative Instrument and Hedging Transactions (Hedging of Precious Metals Inventory) (Details) - USD ($)
$ in Thousands
Sep. 30, 2016
Jun. 30, 2016
Derivatives, Fair Value [Line Items]    
Inventory $ 297,615 $ 245,057
Commemorative coin inventory, held at lower of cost or market (7) (16)
Premium on metals position (3,368) (4,627)
Inventory value not hedged (3,375) (4,643)
Subtotal 294,240 240,414
Commitments at market:    
Open inventory purchase commitments 697,837 550,810
Open inventory sales commitments (229,931) (237,325)
Margin sale commitments (13,598) (12,439)
In-transit inventory no longer subject to market risk (3,326) (7,363)
Unhedgable premiums on open commitment positions 1,478 400
Inventory borrowed from suppliers (4,196) (4,352)
Product financing arrangements (117,789) (59,358)
Advances on industrial metals 4,682 4,521
Inventory subject to price risk 629,397 475,308
Inventory subject to derivative financial instruments    
Market value of derivative financial instruments 627,641 474,979
Net inventory subject to commodity price risk 1,756 329
Precious metals forward contracts at market values    
Inventory subject to derivative financial instruments    
Market value of derivative financial instruments 401,792 188,530
Precious metals futures contracts at market values    
Inventory subject to derivative financial instruments    
Market value of derivative financial instruments $ 225,849 $ 286,449