XML 18 R1.htm IDEA: XBRL DOCUMENT v3.10.0.1
Document And Entity Information - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2018
Feb. 14, 2019
Jun. 30, 2018
Document Information [Line Items]      
Entity Registrant Name CENTURY ALUMINUM CO    
Entity Central Index Key 0000949157    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Filer Category Large Accelerated Filer    
Entity Public Float     $ 782
Entity Common Stock, Shares Outstanding   88,103,440  
Document Fiscal Year Focus 2018    
Document Fiscal Period Focus FY    
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2018    
Entity Emerging Growth Company false    
Entity Small Business false    
Entity Shell Company false