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, 2018
Dec. 31, 2017
Dec. 31, 2018
Dec. 31, 2017
Jun. 30, 2018
Mar. 31, 2016
Schedule Of Financing Arrangements [Line Items]            
Percentage of total expense recognized 31.00%   20.70%      
Liability on borrowed metals $ 227,317,000   $ 227,317,000   $ 280,346,000  
Product financing obligation 82,413,000   82,413,000   113,940,000  
Line of Credit | Trading credit facility            
Schedule Of Financing Arrangements [Line Items]            
Interest expense, notes payable $ 1,900,000 $ 2,000,000 $ 3,900,000 $ 3,700,000    
Percentage of total expense recognized 39.90% 59.20% 47.40% 61.10%    
Effective rate of interest 4.80% 3.81% 4.66% 3.78%    
Line of Credit | Trading credit facility | A-Mark | Trading credit facility            
Schedule Of Financing Arrangements [Line Items]            
Line of credit, current borrowing capacity $ 260,000,000   $ 260,000,000     $ 210,000,000
Line of credit, accordion option           $ 50,000,000
Payments of financing costs     2,600,000      
Accumulated amortization of loan cost $ 200,000   $ 200,000   $ 500,000  
Variable rate basis     one-month LIBOR      
Credit facility, interest rate at period end 2.50%   2.50%   2.09%  
Borrowings due on demand $ 139,000,000   $ 139,000,000   $ 200,000,000  
Borrowings available $ 5,300,000   5,300,000   $ 22,100,000  
Line of credit facility, tangible net worth financial covenant     $ 47,500,000      
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%