XML 154 R1.htm IDEA: XBRL DOCUMENT v3.20.1
Document and Entity Information - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2019
Mar. 12, 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    
Trading Symbol CATC    
Entity Registrant Name CAMBRIDGE BANCORP    
Entity Central Index Key 0000711772    
Current Fiscal Year End Date --12-31    
Entity Filer Category Accelerated Filer    
Entity Well-known Seasoned Issuer No    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Shell Company false    
Entity Emerging Growth Company false    
Entity Small Business false    
Title of 12(b) Security Common Stock    
Security Exchange Name NASDAQ    
Entity Public Float     $ 361.1
Entity Common Stock, Shares Outstanding   5,412,221  
Entity File Number 001-38184    
Entity Incorporation, State or Country Code MA    
Entity Tax Identification Number 04-2777442    
Entity Address, Address Line One 1336 Massachusetts Avenue    
Entity Address, City or Town Cambridge    
Entity Address, State or Province MA    
Entity Address, Postal Zip Code 02138    
City Area Code (617)    
Local Phone Number 876-5500    
Document Annual Report true    
Document Transition Report false    
Documents Incorporated by Reference

Portions of the Registrant’s Definitive Proxy Statement relating to the Annual Meeting of Shareholders, scheduled to be held on May 18, 2020, are incorporated by reference into Part III of this Report.