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