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
3 Months Ended
Sep. 30, 2016
Sep. 30, 2017
Jun. 30, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Secured loan   $ 88,871 $ 91,238
Secured loan, percentage   100.00% 100.00%
Secured loans (current)   $ 88,871 $ 91,238
Bullion and Numismatic      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Secured loans (current)   $ 88,871 $ 91,238
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)   $ 65,909 $ 60,432
Secured loans (current), percentage   74.20% 66.20%
Bullion and Numismatic | Loan-to-value of less than 75%      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Secured loans (current)   $ 22,962 $ 30,806
Secured loans (current), percentage   25.80% 33.80%
Bullion      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Secured loan   $ 57,964 $ 61,767
Secured loan, percentage   65.20% 67.70%
Numismatic and semi-numismatic      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Secured loan   $ 30,907 $ 29,471
Secured loan, percentage   34.80% 32.30%
Minimum      
Accounts, Notes, Loans and Financing Receivable [Line Items]      
Credit quality indicator Loan-to-value threshold percentage 75.00%