A-Mark Precious Metals, Inc. Quarterly report pursuant to Section 13 or 15(d)

Quarterly report pursuant to Section 13 or 15(d)

Summary of Significant Accounting Policies (Narrative) (Details)

Summary of Significant Accounting Policies (Narrative) (Details) (USD $)	0 Months Ended	3 Months Ended		6 Months Ended
	Sep. 19, 2014 tranch	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014 Segment	Dec. 31, 2013	Sep. 25, 2014	Jun. 30, 2014	Feb. 18, 2014
Property, Plant and Equipment [Line Items]
Number of reportable segments				1us-gaap_NumberOfReportableSegments
Premium on metals position		$ 4,653,000		$ 4,653,000			$ 3,285,000
Commemorative coin inventory, held at lower of cost or market		394,000		394,000			2,564,000
Borrowed metals		5,700,000amrk_BorrowedMetals		5,700,000amrk_BorrowedMetals			8,700,000amrk_BorrowedMetals
Inventories loaned under consignment		4,000,000		4,000,000			11,100,000
Product under financing arrangement		80,700,000amrk_ProductUnderFinancingArrangement		80,700,000amrk_ProductUnderFinancingArrangement			24,600,000amrk_ProductUnderFinancingArrangement
Inventory subject to repurchase included in inventory		39,600,000		39,600,000			24,600,000
Ownership percentage								2.50%
Long-term investments		1,611,000us-gaap_CostMethodInvestments		1,611,000us-gaap_CostMethodInvestments			500,000us-gaap_CostMethodInvestments	500,000us-gaap_CostMethodInvestments
Receivable		8,539,000us-gaap_DueFromRelatedParties		8,539,000us-gaap_DueFromRelatedParties			5,852,000us-gaap_DueFromRelatedParties
Long-term receivables		800,000		800,000			0
Payables		17,000		17,000			272,000
Advertising expense		100,000us-gaap_AdvertisingExpense	200,000us-gaap_AdvertisingExpense	300,000us-gaap_AdvertisingExpense	300,000us-gaap_AdvertisingExpense
Shipping, handling costs		1,800,000	1,300,000	3,200,000	3,000,000
Number of tranches	2
Payment for closing of Tranche A	2,000,000
Payments to acquire Tranche A	1,100,000
Payable on closing of Tranche B						900,000
Exclusive supplier agreement, period, Tranche A	5 years
Exclusive supplier agreement, period	3 years
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives of related assets				3 years
Estimated useful lives of intangibles				4 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives of related assets				5 years
Estimated useful lives of intangibles				15 years
Common Class A
Property, Plant and Equipment [Line Items]
Agreement to purchase noncontrolling interest, percentage	9.00%
Percentage of stock to be purchased for Tranche A	5.00%
Percentage of stock to be purchased for Tranche B	4.00%
Cost-method Investee
Property, Plant and Equipment [Line Items]
Receivable		18,300,000		18,300,000			2,600,000
Secured loans		1,000,000		1,000,000			0
Long-term receivables		800,000		800,000
Payables		26,100,000		26,100,000			3,500,000
Revenue from related party		139,400,000	46,900,000	227,400,000	83,200,000
Purchases from related party		$ 0	$ 1,900,000	$ 400,000	$ 1,900,000