Quarterly report pursuant to Section 13 or 15(d)

Inventories (Summary of Inventories) (Details)

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Inventories (Summary of Inventories) (Details) - USD ($)
$ in Thousands
Sep. 30, 2017
Jun. 30, 2017
Inventory [Line Items]    
Inventories $ 186,720 $ 149,316
Restricted inventories 124,864 135,343
Restricted and Nonrestricted Inventory, Net 311,584 284,659
Inventory held for sale    
Inventory [Line Items]    
Inventories 58,746 43,787
Repurchase arrangements with customers    
Inventory [Line Items]    
Inventories 104,986 92,496
Consignment arrangements with customers    
Inventory [Line Items]    
Inventories 7,763 7,368
Commemorative coins, held at lower of cost or market    
Inventory [Line Items]    
Inventories 215 40
Borrowed precious metals from suppliers    
Inventory [Line Items]    
Inventories 15,010 5,625
Product financing arrangement, restricted    
Inventory [Line Items]    
Restricted inventories $ 124,864 $ 135,343