Quarterly report pursuant to Section 13 or 15(d)

Financing Agreements (Details)

v3.10.0.1
Financing Agreements (Details) - USD ($)
 3 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Jun. 30, 2018
Mar. 31, 2016
Schedule Of Financing Arrangements [Line Items]        
Percentage of total expense recognized 7.20%      
Liability on borrowed metals $ 227,198,000   $ 280,346,000  
Product financing obligation 53,126,000   113,940,000  
Line of Credit | Trading credit facility        
Schedule Of Financing Arrangements [Line Items]        
Interest expense, notes payable $ 2,000,000 $ 1,700,000    
Percentage of total expense recognized 57.20% 63.50%    
Effective rate of interest 4.54% 3.75%    
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 $ 300,000   $ 500,000  
Variable rate basis one-month LIBOR      
Credit facility, interest rate at period end 2.26%   2.09%  
Borrowings due on demand $ 179,000,000   $ 200,000,000  
Borrowings available 3,500,000   $ 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%