Document and Entity Information
3 Months Ended
Mar. 31, 2012
May 04, 2012
Document and Entity Information [Abstract]    
Entity Registrant Name MRC GLOBAL INC.  
Entity Central Index Key 0001439095  
Document Type 10-Q  
Document Period End Date Mar. 31, 2012  
Amendment Flag false  
Document Fiscal Year Focus 2012  
Document Fiscal Period Focus Q1  
Current Fiscal Year End Date --12-31  
Entity Filer Category Non-accelerated Filer  
Entity Common Stock, Shares Outstanding   101,487,000