Annual report pursuant to Section 13 and 15(d)

Financing Agreements (Details)

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Financing Agreements (Details) - USD ($)
 12 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Mar. 31, 2016
Schedule Of Financing Arrangements [Line Items]      
Interest expense, notes payable $ 648,000    
Percentage of total expense recognized 4.70%    
Effective rate of interest 9.25%    
Liability on borrowed metals $ 280,346,000 $ 5,625,000  
Product financing obligation 113,940,000 135,343,000  
Line of Credit | Trading credit facility      
Schedule Of Financing Arrangements [Line Items]      
Interest expense, notes payable $ 7,900,000 $ 6,400,000  
Percentage of total expense recognized 57.00% 63.60%  
Effective rate of interest 3.96% 3.18%  
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   $ 210,000,000
Line of credit, accordion option     $ 50,000,000
Payments of financing costs 2,600,000    
Accumulated amortization of loan cost $ 500,000 $ 100,000  
Variable rate basis one-month LIBOR    
Credit facility, interest rate at period end 2.09% 1.17%  
Borrowings due on demand $ 200,000,000 $ 180,000,000  
Borrowings available 22,100,000 $ 45,600,000  
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%