Quarterly report pursuant to Section 13 or 15(d)

Receivables (Narrative) (Details)

v2.4.1.9
Receivables (Narrative) (Details) (USD $)
6 Months Ended 0 Months Ended
Dec. 31, 2014
class
loan
Dec. 31, 2013
Sep. 27, 2013
Jul. 02, 2014
Jun. 30, 2014
loan
Jun. 18, 2014
Jun. 05, 2014
Oct. 09, 2014
Jan. 23, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]                  
Loans receivable average effective rate of interest (percentage) 8.30%amrk_LoansReceivableAverageEffectiveRateOfInterest 7.90%amrk_LoansReceivableAverageEffectiveRateOfInterest              
Short term loan receivable       $ 3,700,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount   $ 2,600,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount $ 3,800,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount    
Option to extend maturity 180 days                
Classes of receivables 3amrk_ClassesOfReceivables                
Loans receivable payment terms for interest 30 days                
Delinquent period 30 days                
Loan receivable liquidation period post default 90 days                
Number of loans 2amrk_FinanceReceivableNumberofLoans       0amrk_FinanceReceivableNumberofLoans        
Minimum                  
Accounts, Notes, Loans and Financing Receivable [Line Items]                  
Credit quality indicator Loan-to-value threshold percentage 75.00%amrk_CreditQualityIndicatorLoanToValueThresholdPercentage
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
               
Maximum                  
Accounts, Notes, Loans and Financing Receivable [Line Items]                  
Secured loans-to-value percentage 100.00%amrk_SecuredLoansToValuePercentage
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
               
Collateral Finance Corporation                  
Accounts, Notes, Loans and Financing Receivable [Line Items]                  
Short term loan receivable 3,000,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ dei_LegalEntityAxis
= amrk_CollateralFinanceCorporationMember
  12,800,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ dei_LegalEntityAxis
= amrk_CollateralFinanceCorporationMember
           
Payments to acquire loans receivable     400,000us-gaap_PaymentsToAcquireLoansReceivable
/ dei_LegalEntityAxis
= amrk_CollateralFinanceCorporationMember
           
Stack Bowers Galleries                  
Accounts, Notes, Loans and Financing Receivable [Line Items]                  
Short term loan receivable 0us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amrk_StackBowersGalleriesMember
      2,600,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amrk_StackBowersGalleriesMember
2,600,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amrk_StackBowersGalleriesMember
     
Rate of interest (percentage)           5.50%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amrk_StackBowersGalleriesMember
     
Collateral Finance Corporation                  
Accounts, Notes, Loans and Financing Receivable [Line Items]                  
Short term loan receivable         5,800,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amrk_CollateralFinanceCorporationMember
       
Premium on receivable 200,000us-gaap_ReceivableWithImputedInterestPremium
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amrk_CollateralFinanceCorporationMember
      300,000us-gaap_ReceivableWithImputedInterestPremium
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amrk_CollateralFinanceCorporationMember
       
Rights Assumed for Portfolio on July 1, 2014 | Collateral Finance Corporation                  
Accounts, Notes, Loans and Financing Receivable [Line Items]                  
Short term loan receivable 2,000,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ dei_LegalEntityAxis
= amrk_CollateralFinanceCorporationMember
/ us-gaap_RelatedPartyTransactionAxis
= amrk_RightsAssumedforPortfolioonJulyFirstTwentyFourteenMember
               
Collateral Finance Corporation | Rights Assumed for Portfolio on June 5, 2014                  
Accounts, Notes, Loans and Financing Receivable [Line Items]                  
Short term loan receivable 1,300,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis
= amrk_CollateralFinanceCorporationMember
/ us-gaap_RelatedPartyTransactionAxis
= amrk_RightsAssumedforPortfolioonJuneFifthTwentyFourteenMember
      3,800,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_AccountsNotesLoansAndFinancingReceivablesByLegalEntityOfCounterpartyTypeAxis
= amrk_CollateralFinanceCorporationMember
/ us-gaap_RelatedPartyTransactionAxis
= amrk_RightsAssumedforPortfolioonJuneFifthTwentyFourteenMember
       
Line of Credit [Member] | Stack Bowers Galleries                  
Accounts, Notes, Loans and Financing Receivable [Line Items]                  
Short term loan receivable 5,300,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amrk_StackBowersGalleriesMember
               
Line of credit, maximum borrowing capacity               16,000,000.0us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_LineOfCreditMember
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= amrk_StackBowersGalleriesMember
 
Subsequent Event [Member]                  
Accounts, Notes, Loans and Financing Receivable [Line Items]                  
Short term loan receivable                 $ 3,100,000us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
/ us-gaap_SubsequentEventTypeAxis
= us-gaap_SubsequentEventMember