Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

v3.10.0.1
Document and Entity Information - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Feb. 18, 2019
Jun. 30, 2018
Document And Entity Information [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2018    
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY    
Trading Symbol BRSS    
Entity Registrant Name GLOBAL BRASS & COPPER HOLDINGS, INC.    
Entity Central Index Key 0001533526    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer No    
Entity Current Reporting Status Yes    
Entity Voluntary Filers No    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Filer Category Accelerated Filer    
Entity Common Stock, Shares Outstanding   21,880,908  
Entity Public Float     $ 674.2