Quarterly report pursuant to Section 13 or 15(d)

Financing Agreements (Details)

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Financing Agreements (Details) - USD ($)
 3 Months Ended
Sep. 30, 2017
Sep. 30, 2016
Jun. 30, 2017
Mar. 31, 2016
Schedule Of Financing Arrangements [Line Items]        
Interest expense, notes payable $ 79,000      
Percentage of total expense recognized 2.90%      
Liability on borrowed metals $ 15,010,000   $ 5,625,000  
Product financing obligation 124,864,000   135,343,000  
Line of Credit | Trading credit facility        
Schedule Of Financing Arrangements [Line Items]        
Interest expense, notes payable $ 1,500,000 $ 1,700,000    
Percentage of total expense recognized 65.00% 63.50%    
Effective rate of interest 2.98% 3.75%    
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 1,900,000      
Accumulated amortization of loan cost $ 600,000   $ 100,000  
Variable rate basis one-month LIBOR      
Credit facility, interest rate at period end 1.17%   1.23%  
Borrowings due on demand $ 180,000,000   $ 219,000,000  
Credit facility, remaining borrowing capacity $ 45,600,000   $ 30,000,000  
LIBOR | Line of Credit | Revolving Credit Facility        
Schedule Of Financing Arrangements [Line Items]        
Variable rate 2.50%      
LIBOR | Line of Credit | Bridge Loan        
Schedule Of Financing Arrangements [Line Items]        
Variable rate 4.50%