Quarterly report pursuant to Section 13 or 15(d)

Secured Loans Receivable (Loans Receivable and Credit Quality Indicators) (Details)

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Secured Loans Receivable (Loans Receivable and Credit Quality Indicators) (Details) - USD ($)
$ in Thousands
Sep. 30, 2018
Jun. 30, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Secured loan $ 81,891 $ 110,424
Secured loan, percentage 100.00% 100.00%
Secured loans (current) [1] $ 81,891 $ 110,424
Bullion and Numismatic    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Secured loans (current) $ 81,891 $ 110,424
Secured loans (current), percentage 100.00% 100.00%
Bullion and Numismatic | Loan-to-value of 75% or more    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Secured loans (current) $ 50,307 $ 69,629
Secured loans (current), percentage 61.40% 63.10%
Bullion and Numismatic | Loan-to-value of less than 75%    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Secured loans (current) $ 31,584 $ 40,795
Secured loans (current), percentage 38.60% 36.90%
Bullion    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Secured loan $ 51,015 $ 72,128
Secured loan, percentage 62.30% 65.30%
Numismatic and semi-numismatic    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Secured loan $ 30,876 $ 38,296
Secured loan, percentage 37.70% 34.70%
[1] Includes amounts of the consolidated variable interest entity, which is presented separately in the table below.