Quarterly report pursuant to Section 13 or 15(d)

Hedging Transactions (Hedging of Precious Metals Inventory) (Details)

v2.4.1.9
Hedging Transactions (Hedging of Precious Metals Inventory) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Jun. 30, 2014
Derivatives, Fair Value [Line Items]    
Inventory $ 223,771us-gaap_InventoryFinishedGoods $ 175,554us-gaap_InventoryFinishedGoods
Commemorative coin inventory, held at lower of cost or market (394)amrk_InventoryCommemorativeCoinStatedAtLowerCostOrMarket (2,564)amrk_InventoryCommemorativeCoinStatedAtLowerCostOrMarket
Premium on metals position (4,653)amrk_InventoryPurchasePremiumOnMetalsPositionmarkedtomarket (3,285)amrk_InventoryPurchasePremiumOnMetalsPositionmarkedtomarket
Inventory value not hedged (5,047)amrk_InventoryPurchasePremiumOnMetalsPositionTotalMTMLCM (5,849)amrk_InventoryPurchasePremiumOnMetalsPositionTotalMTMLCM
Subtotal 218,724amrk_PhysicalInventoryNetOfPurchasePremiums 169,705amrk_PhysicalInventoryNetOfPurchasePremiums
Commitments at market    
Open inventory purchase commitments 441,431amrk_OpenInventoryPurchaseCommitments 489,944amrk_OpenInventoryPurchaseCommitments
Open inventory sales commitments (204,389)amrk_OpenInventorySaleCommitments (190,108)amrk_OpenInventorySaleCommitments
Margin sale commitments (13,073)amrk_MarginSaleCommitments (15,751)amrk_MarginSaleCommitments
In-transit inventory no longer subject to market risk (11,136)amrk_DeferredLiabilityNotSubjectToMarketRisk (4,522)amrk_DeferredLiabilityNotSubjectToMarketRisk
Unhedgable premiums on open commitment positions 2,410amrk_UnhedgablePremiumsOnOpenCommitmentPositions 1,694amrk_UnhedgablePremiumsOnOpenCommitmentPositions
Inventory borrowed from suppliers (5,684)amrk_InventoryBorrowedFromSuppliers (8,709)amrk_InventoryBorrowedFromSuppliers
Product financing obligation (80,660)amrk_ObligationUnderProductFinancingAgreement (24,610)amrk_ObligationUnderProductFinancingAgreement
Advances on industrial metals 3,141amrk_AdvancesPaymentsOnIndustrialMetals 8,813amrk_AdvancesPaymentsOnIndustrialMetals
Inventory subject to price risk 350,764amrk_InventorySubjectToPriceRisk 426,456amrk_InventorySubjectToPriceRisk
Inventory subject to derivative financial instruments    
Market value of derivative financial instruments 350,468invest_DerivativeNotionalAmount 427,039invest_DerivativeNotionalAmount
Net inventory subject to commodity price risk 296amrk_NetInventorySubjectToPriceRisk (583)amrk_NetInventorySubjectToPriceRisk
Precious metals forward contracts at market values    
Inventory subject to derivative financial instruments    
Market value of derivative financial instruments 168,577invest_DerivativeNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForwardContractsMember 		206,055invest_DerivativeNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_ForwardContractsMember
Precious metals futures contracts at market values    
Inventory subject to derivative financial instruments    
Market value of derivative financial instruments $ 181,891invest_DerivativeNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_FutureMember 		$ 220,984invest_DerivativeNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= us-gaap_FutureMember