v3.8.0.1
Document and Entity Information - shares
3 Months Ended
Sep. 30, 2017
Nov. 09, 2017
Document and Entity Information [Abstract]    
Entity Registrant Name A-Mark Precious Metals, Inc.  
Entity Central Index Key 0001591588  
Trading Symbol AMRK  
Current Fiscal Year End Date --06-30  
Entity Filer Category Smaller Reporting Company  
Document Type 10-Q  
Document Period End Date Sep. 30, 2017  
Document Fiscal Year Focus 2018  
Document Fiscal Period Focus Q1  
Amendment Flag false  
Entity Common Stock, Shares Outstanding   7,031,450