Document And Entity Information - shares
3 Months Ended
Mar. 31, 2019
Apr. 30, 2019
Document And Entity Information [Abstract]    
Entity Registrant Name CAI International, Inc.  
Entity Filer Category Accelerated Filer  
Entity Central Index Key 0001388430  
Amendment Flag false  
Document Type 10-Q  
Document Fiscal Period Focus Q1  
Trading Symbol cai  
Document Period End Date Mar. 31, 2019  
Document Fiscal Year Focus 2019  
Current Fiscal Year End Date --12-31  
Entity Common Stock, Shares Outstanding   17,934,992
Entity Emerging Growth Company false  
Entity Small Business false