Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies (Customer Concentrations) (Details)

v2.4.1.9
Summary of Significant Accounting Policies (Customer Concentrations) (Details) (USD $)
3 Months Ended 6 Months Ended 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2014
Dec. 31, 2013
Jun. 30, 2014
Concentration Risk [Line Items]          
Total revenue $ 1,538,871,000us-gaap_SalesRevenueGoodsNet $ 1,488,691,000us-gaap_SalesRevenueGoodsNet $ 2,992,337,000us-gaap_SalesRevenueGoodsNet $ 2,984,716,000us-gaap_SalesRevenueGoodsNet  
Total accounts receivable, net (excluding secured loans and derivative assets) 65,360,000amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps   65,360,000amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps   39,409,000amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps
Derivative asset 18,112,000us-gaap_DerivativeAssets   18,112,000us-gaap_DerivativeAssets   22,184,000us-gaap_DerivativeAssets
Revenue | Customer concentrations          
Concentration Risk [Line Items]          
Total revenue 1,538,871,000us-gaap_SalesRevenueGoodsNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
1,488,691,000us-gaap_SalesRevenueGoodsNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
2,992,337,000us-gaap_SalesRevenueGoodsNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
2,984,716,000us-gaap_SalesRevenueGoodsNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
 
Concentration risk, percentage 100.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
100.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
  100.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
 
Accounts receivable | Customer concentrations          
Concentration Risk [Line Items]          
Total accounts receivable, net (excluding secured loans and derivative assets) 65,360,000amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
  65,360,000amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
  39,409,000amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
Concentration risk, percentage     100.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
100.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
 
Secured loans | Customer concentrations          
Concentration Risk [Line Items]          
Total secured loans 42,564,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
  42,564,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
  41,261,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
Concentration risk, percentage     100.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
  100.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
Sunshine Mint | Accounts receivable | Customer concentrations          
Concentration Risk [Line Items]          
Total accounts receivable, net (excluding secured loans and derivative assets) 9,680,000amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_SunshineMintMember
  9,680,000amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_SunshineMintMember
  0amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_SunshineMintMember
Concentration risk, percentage     14.80%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_SunshineMintMember
0.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_SunshineMintMember
 
HSBC Bank USA | Revenue | Customer concentrations          
Concentration Risk [Line Items]          
Total revenue 448,453,000us-gaap_SalesRevenueGoodsNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_HSBCBankUSAMember
393,148,000us-gaap_SalesRevenueGoodsNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_HSBCBankUSAMember
982,991,000us-gaap_SalesRevenueGoodsNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_HSBCBankUSAMember
705,693,000us-gaap_SalesRevenueGoodsNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_HSBCBankUSAMember
 
Concentration risk, percentage 29.10%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_HSBCBankUSAMember
26.40%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_HSBCBankUSAMember
32.90%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_HSBCBankUSAMember
23.60%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_HSBCBankUSAMember
 
US Mint | Accounts receivable | Customer concentrations          
Concentration Risk [Line Items]          
Total accounts receivable, net (excluding secured loans and derivative assets) 18,839,000amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_UnitedStatesMintMember
  18,839,000amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_UnitedStatesMintMember
  0amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_UnitedStatesMintMember
Concentration risk, percentage     28.80%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_UnitedStatesMintMember
0.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_UnitedStatesMintMember
 
Customer A | Secured loans | Customer concentrations          
Concentration Risk [Line Items]          
Total secured loans 5,273,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomerMember
  5,273,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomerMember
  2,562,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomerMember
Concentration risk, percentage     12.40%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomerMember
  6.20%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomerMember
Customer B | Secured loans | Customer concentrations          
Concentration Risk [Line Items]          
Total secured loans 4,900,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomerBMember
  4,900,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomerBMember
  4,200,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomerBMember
Concentration risk, percentage     11.50%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomerBMember
  10.20%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomerBMember
Customer C | Secured loans | Customer concentrations          
Concentration Risk [Line Items]          
Total secured loans 4,391,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomercMember
  4,391,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomercMember
  4,103,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomercMember
Concentration risk, percentage     10.30%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomercMember
  9.90%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_CustomercMember
Major Customers | Revenue | Customer concentrations          
Concentration Risk [Line Items]          
Total revenue 448,453,000us-gaap_SalesRevenueGoodsNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
393,148,000us-gaap_SalesRevenueGoodsNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
982,991,000us-gaap_SalesRevenueGoodsNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
705,693,000us-gaap_SalesRevenueGoodsNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
 
Concentration risk, percentage 29.10%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
26.40%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
32.90%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
23.60%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_SalesRevenueGoodsNetMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
 
Major Customers | Accounts receivable | Customer concentrations          
Concentration Risk [Line Items]          
Total accounts receivable, net (excluding secured loans and derivative assets) 28,519,000amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
  28,519,000amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
  0amrk_ReceivablesExcludingSecuredLoansDerivativeAssetsGrossTradingOps
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
Concentration risk, percentage     43.60%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
0.00%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_AccountsReceivableMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
 
Major Customers | Secured loans | Customer concentrations          
Concentration Risk [Line Items]          
Total secured loans $ 14,564,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
  $ 14,564,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
  $ 10,865,000us-gaap_NotesReceivableNet
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
Concentration risk, percentage     34.20%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember
  26.30%us-gaap_ConcentrationRiskPercentage1
/ us-gaap_ConcentrationRiskByBenchmarkAxis
= us-gaap_LoansAndFinanceReceivablesMember
/ us-gaap_ConcentrationRiskByTypeAxis
= us-gaap_CustomerConcentrationRiskMember
/ us-gaap_MajorCustomersAxis
= amrk_MajorCustomersMember