Annual report pursuant to Section 13 and 15(d)

Document and Entity Information

Document and Entity Information - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Mar. 02, 2020
Jun. 30, 2019
Cover [Abstract]      
Document Type 10-K    
Amendment Flag false    
Document Period End Date Dec. 31, 2019    
Document Fiscal Year Focus 2019    
Document Fiscal Period Focus FY    
Entity Central Index Key 0001383701    
Current Fiscal Year End Date --12-31    
Entity Well-known Seasoned Issuer No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Voluntary Filers No    
Entity Filer Category Non-accelerated Filer    
Entity Small Business true    
Entity Emerging Growth Company false    
Entity Shell Company false    
Title of 12(b) Security Common Stock, par value $0.0001 per share    
Trading Symbol CNAT    
Security Exchange Name NASDAQ    
Entity Incorporation, State or Country Code DE    
Entity Address, Address Line One 16745 West Bernardo Dr.    
Entity Address, Address Line Two Suite 250    
Entity Address, City or Town San Diego    
Entity Address, State or Province CA    
Entity Address, Postal Zip Code 92127    
City Area Code (858)    
Local Phone Number 376-2600    
Entity File Number 001-36003    
Entity Tax Identification Number 20-3183915    
Entity Common Stock, Shares Outstanding   33,170,487  
Entity Public Float     $ 8.4
Document Annual Report true    
Document Transition Report false