Shareholders' Equity (Tables)

3 Months Ended

Mar. 31, 2022

Equity [Abstract]

Schedule of Minimum Capital Requirements Considered Well Capitalized by FRB and FDIC

As of March 31, 2022 and December 31, 2021, the Company and the Bank met all applicable minimum capital requirements and were considered “well-capitalized” by both the Federal Reserve Bank (“FRB”) and the Federal Deposit Insurance Corporation (“FDIC”).

	Actual					Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer					Minimum To Be Well-Capitalized Under Prompt Corrective Action Provisions
	Amount		Ratio			Amount		Ratio			Amount		Ratio
	(dollars in thousands)
At March 31, 2022
Cambridge Bancorp:
Total capital (to risk-weighted assets)	$	428,313		13.5	%	$	332,832		10.5	%	N/A		N/A
Tier 1 capital (to risk-weighted assets)		392,831		12.4	%		269,435		8.5	%	N/A		N/A
Common equity tier I capital (to risk-weighted assets)		392,831		12.4	%		221,888		7.0	%	N/A		N/A
Tier 1 capital (to average assets)		392,831		8.0	%		196,394		4.0	%	N/A		N/A
Cambridge Trust Company:
Total capital (to risk-weighted assets)	$	412,721		13.0	%	$	332,802		10.5	%	$	316,954		10.0	%
Tier 1 capital (to risk-weighted assets)		377,239		11.9	%		269,411		8.5	%		253,563		8.0	%
Common equity tier I capital (to risk-weighted assets)		377,239		11.9	%		221,868		7.0	%		206,020		6.5	%
Tier 1 capital (to average assets)		377,239		7.7	%		196,383		4.0	%		245,479		5.0	%

	Actual					Minimum Capital Required For Capital Adequacy Plus Capital Conservation Buffer					Minimum To Be Well-Capitalized Under Prompt Corrective Action Provisions
	Amount		Ratio			Amount		Ratio			Amount		Ratio
	(dollars in thousands)
At December 31, 2021
Cambridge Bancorp:
Total capital (to risk-weighted assets)	$	420,398		13.6	%	$	325,617		10.5	%	N/A		N/A
Tier 1 capital (to risk-weighted assets)		384,518		12.4	%		263,595		8.5	%	N/A		N/A
Common equity tier I capital (to risk-weighted assets)		384,518		12.4	%		217,078		7.0	%	N/A		N/A
Tier 1 capital (to average assets)		384,518		8.3	%		185,015		4.0	%	N/A		N/A
Cambridge Trust Company:
Total capital (to risk-weighted assets)	$	409,806		13.2	%	$	325,587		10.5	%	$	310,082		10.0	%
Tier 1 capital (to risk-weighted assets)		373,926		12.1	%		263,570		8.5	%		248,066		8.0	%
Common equity tier I capital (to risk-weighted assets)		373,926		12.1	%		217,058		7.0	%		201,554		6.5	%
Tier 1 capital (to average assets)		373,926		8.1	%		185,003		4.0	%		231,254		5.0	%