Quarterly report pursuant to Section 13 or 15(d)

Financing Agreements (Details)

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Financing Agreements (Details) - USD ($)
 3 Months Ended 6 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Jun. 30, 2017
Mar. 31, 2016
Schedule Of Financing Arrangements [Line Items]            
Interest expense, notes payable $ 200,000   $ 279,000      
Percentage of total expense recognized 6.00%   4.60%      
Effective rate of interest 9.29%   9.33%      
Liability on borrowed metals $ 19,526,000   $ 19,526,000   $ 5,625,000  
Product financing obligation 120,161,000   120,161,000   135,343,000  
Line of Credit | Trading credit facility            
Schedule Of Financing Arrangements [Line Items]            
Interest expense, notes payable $ 2,000,000 $ 1,600,000 $ 3,700,000 $ 3,000,000    
Percentage of total expense recognized 59.20% 63.50% 61.10% 64.20%    
Effective rate of interest 3.81% 3.36% 3.17% 3.78%    
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   $ 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 $ 300,000   $ 300,000   $ 100,000  
Variable rate basis     one-month LIBOR      
Credit facility, interest rate at period end 1.56%   1.56%   1.17%  
Borrowings due on demand $ 214,000,000   $ 214,000,000   $ 180,000,000  
Credit facility, remaining borrowing capacity $ 35,900,000   $ 35,900,000   $ 45,600,000  
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%