Quarterly report pursuant to Section 13 or 15(d)

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

v2.4.1.9
Receivables (Loans Receivable and Credit Quality Indicators) (Details) (USD $)
In Thousands, unless otherwise specified
 6 Months Ended
Dec. 31, 2014
class
Jun. 30, 2014
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Classes of receivables 3amrk_ClassesOfReceivables  
Secured loan $ 42,564us-gaap_LoansReceivableNet $ 41,261us-gaap_LoansReceivableNet
Secured loan, percentage 100.00%amrk_PercentageOfLoansReceivable 100.00%amrk_PercentageOfLoansReceivable
Secured loans (current) 41,764us-gaap_NotesAndLoansReceivableNetCurrent 41,261us-gaap_NotesAndLoansReceivableNetCurrent
Loan-to-value of more than 100%    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Secured loan 193us-gaap_LoansReceivableNet
/ us-gaap_InternalCreditAssessmentAxis
= amrk_LoantovalueofMoreThanHundredPercentMember 		 
Secured loan, percentage 0.50%amrk_PercentageOfLoansReceivable
/ us-gaap_InternalCreditAssessmentAxis
= amrk_LoantovalueofMoreThanHundredPercentMember 		 
Bullion and Numismatic    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Secured loan 36,291us-gaap_LoansReceivableNet
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember 		41,261us-gaap_LoansReceivableNet
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember
Secured loan, percentage 85.30%amrk_PercentageOfLoansReceivable
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember 		100.00%amrk_PercentageOfLoansReceivable
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember
Secured loans (current) 36,291us-gaap_NotesAndLoansReceivableNetCurrent
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember 		41,261us-gaap_NotesAndLoansReceivableNetCurrent
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember
Secured loans (current), percentage 100.00%amrk_NotesLoansandFinancingReceivablePercentageofTotal
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember 		100.00%amrk_NotesLoansandFinancingReceivablePercentageofTotal
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember
Bullion and Numismatic | Loan-to-value of 75% or more    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Secured loans (current) 15,647us-gaap_NotesAndLoansReceivableNetCurrent
/ us-gaap_InternalCreditAssessmentAxis
= amrk_LoanToValueOfSeventyFivePercentOrMoreMember
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember 		11,950us-gaap_NotesAndLoansReceivableNetCurrent
/ us-gaap_InternalCreditAssessmentAxis
= amrk_LoanToValueOfSeventyFivePercentOrMoreMember
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember
Secured loans (current), percentage 43.10%amrk_NotesLoansandFinancingReceivablePercentageofTotal
/ us-gaap_InternalCreditAssessmentAxis
= amrk_LoanToValueOfSeventyFivePercentOrMoreMember
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember 		29.00%amrk_NotesLoansandFinancingReceivablePercentageofTotal
/ us-gaap_InternalCreditAssessmentAxis
= amrk_LoanToValueOfSeventyFivePercentOrMoreMember
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember
Bullion and Numismatic | Loan-to-value of less than 75%    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Secured loans (current) 20,644us-gaap_NotesAndLoansReceivableNetCurrent
/ us-gaap_InternalCreditAssessmentAxis
= amrk_LoanToValueOfLessThanSeventyFivePercentMember
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember 		29,311us-gaap_NotesAndLoansReceivableNetCurrent
/ us-gaap_InternalCreditAssessmentAxis
= amrk_LoanToValueOfLessThanSeventyFivePercentMember
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember
Secured loans (current), percentage 56.90%amrk_NotesLoansandFinancingReceivablePercentageofTotal
/ us-gaap_InternalCreditAssessmentAxis
= amrk_LoanToValueOfLessThanSeventyFivePercentMember
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember 		71.00%amrk_NotesLoansandFinancingReceivablePercentageofTotal
/ us-gaap_InternalCreditAssessmentAxis
= amrk_LoanToValueOfLessThanSeventyFivePercentMember
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionandNumismaticMember
Bullion    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Secured loan 9,960us-gaap_LoansReceivableNet
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionFinancingReceivableMember 		17,361us-gaap_LoansReceivableNet
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionFinancingReceivableMember
Secured loan, percentage 23.40%amrk_PercentageOfLoansReceivable
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionFinancingReceivableMember 		42.10%amrk_PercentageOfLoansReceivable
/ us-gaap_UnderlyingAssetClassAxis
= amrk_BullionFinancingReceivableMember
Numismatic and semi numismatic    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Secured loan 26,331us-gaap_LoansReceivableNet
/ us-gaap_UnderlyingAssetClassAxis
= amrk_NumismaticandSemiNumismaticMember 		23,900us-gaap_LoansReceivableNet
/ us-gaap_UnderlyingAssetClassAxis
= amrk_NumismaticandSemiNumismaticMember
Secured loan, percentage 61.90%amrk_PercentageOfLoansReceivable
/ us-gaap_UnderlyingAssetClassAxis
= amrk_NumismaticandSemiNumismaticMember 		57.90%amrk_PercentageOfLoansReceivable
/ us-gaap_UnderlyingAssetClassAxis
= amrk_NumismaticandSemiNumismaticMember
Other pledged assets    
Accounts, Notes, Loans and Financing Receivable [Line Items]    
Secured loan $ 6,273us-gaap_LoansReceivableNet
/ us-gaap_UnderlyingAssetClassAxis
= amrk_AssetsNotExclusivelyPreciousMetalsMember 		$ 0us-gaap_LoansReceivableNet
/ us-gaap_UnderlyingAssetClassAxis
= amrk_AssetsNotExclusivelyPreciousMetalsMember
Secured loan, percentage 14.70%amrk_PercentageOfLoansReceivable
/ us-gaap_UnderlyingAssetClassAxis
= amrk_AssetsNotExclusivelyPreciousMetalsMember 		0.00%amrk_PercentageOfLoansReceivable
/ us-gaap_UnderlyingAssetClassAxis
= amrk_AssetsNotExclusivelyPreciousMetalsMember