Document And Entity Information - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Jan. 31, 2019
Jun. 29, 2018
Document And Entity Information [Abstract]      
Entity Registrant Name CAI International, Inc.    
Entity Filer Category Accelerated Filer    
Entity Central Index Key 0001388430    
Entity Current Reporting Status Yes    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Amendment Flag false    
Document Type 10-K    
Document Fiscal Period Focus FY    
Trading Symbol cai    
Document Period End Date Dec. 31, 2018    
Document Fiscal Year Focus 2018    
Current Fiscal Year End Date --12-31    
Entity Common Stock, Shares Outstanding   18,712,252  
Entity Public Float     $ 382.8
Entity Emerging Growth Company false    
Entity Small Business false    
Entity Shell Company false