Shareholders' Equity (Tables)

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

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

The Company’s and the Bank’s actual and required capital measures were as follows:

	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	%

	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, 2020
Cambridge Bancorp:
Total capital (to risk-weighted assets)	$	378,393		13.9	%	$	285,145		10.5	%	N/A		N/A
Tier 1 capital (to risk-weighted assets)		344,409		12.7	%		230,832		8.5	%	N/A		N/A
Common equity tier I capital (to risk-weighted assets)		344,409		12.7	%		190,097		7.0	%	N/A		N/A
Tier 1 capital (to average assets)		344,409		8.9	%		155,009		4.0	%	N/A		N/A
Cambridge Trust Company:
Total capital (to risk-weighted assets)	$	376,209		13.9	%	$	285,117		10.5	%	$	271,540		10.0	%
Tier 1 capital (to risk-weighted assets)		342,229		12.6	%		230,809		8.5	%		217,232		8.0	%
Common equity tier I capital (to risk-weighted assets)		342,229		12.6	%		190,078		7.0	%		176,501		6.5	%
Tier 1 capital (to average assets)		342,229		8.8	%		154,999		4.0	%		193,748		5.0	%