Annual report pursuant to Section 13 and 15(d)

Financing Agreements (Narrative) (Details)

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Financing Agreements (Narrative) (Details) - USD ($)
 12 Months Ended
Jun. 30, 2016
Jun. 30, 2015
Mar. 31, 2016
Schedule Of Financing Arrangements [Line Items]      
Liability on borrowed metals $ 4,352,000 $ 9,500,000  
Product financing obligation 59,358,000 39,425,000  
Line of Credit | Trading credit facility      
Schedule Of Financing Arrangements [Line Items]      
Interest expense, notes payable $ 4,900,000 $ 3,600,000  
Percentage of total expense recognized 77.90% 83.20%  
Effective rate of interest (percentage) 2.83% 2.82%  
Line of Credit | Trading credit facility | A-Mark | Trading credit facility      
Schedule Of Financing Arrangements [Line Items]      
Line of credit, maximum borrowing capacity     $ 275,000,000
Line of credit, current borrowing capacity     225,000,000
Line of credit, accordion option     $ 50,000,000
Payments of Financing Costs $ 800,000    
Accumulated Amortization of Debt Issuance Costs, Line of Credit Arrangements $ 600,000 $ 0  
Variable rate basis one-month LIBOR    
Credit facility, interest rate at period end (percentage) 0.47% 0.19%  
Borrowings due on demand $ 212,000,000 $ 147,000,000  
Credit facility, remaining borrowing capacity 17,800,000 $ 20,900,000  
Credit facility, minimum required tangible net worth $ 35,000,000    
LIBOR | Line of Credit | Revolving Credit Facility      
Schedule Of Financing Arrangements [Line Items]      
Variable rate (percentage) 2.50%    
LIBOR | Line of Credit | Bridge Loan      
Schedule Of Financing Arrangements [Line Items]      
Variable rate (percentage) 4.50%