v3.5.0.2
Document and Entity Information - shares
6 Months Ended
Jun. 30, 2016
Jul. 22, 2016
Document Type 10-Q  
Amendment Flag false  
Document Period End Date Jun. 30, 2016  
Document Fiscal Year Focus 2016  
Document Fiscal Period Focus Q2  
Entity Registrant Name MRC GLOBAL INC.  
Entity Central Index Key 0001439095  
Current Fiscal Year End Date --12-31  
Entity Filer Category Large Accelerated Filer  
Common Stock [Member]    
Entity Common Stock, Shares Outstanding   96,395,357
Restricted Stock [Member]    
Entity Common Stock, Shares Outstanding   570,845