Shareholders' Equity (Tables)

12 Months Ended

Dec. 31, 2022

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, 2022
Cambridge Bancorp:
Total capital (to risk-weighted assets)	$	506,239		13.5	%	$	393,285		10.5	%	N/A		N/A
Tier 1 capital (to risk-weighted assets)		466,369		12.5	%		318,373		8.5	%	N/A		N/A
Common equity tier I capital (to risk-weighted assets)		466,369		12.5	%		262,190		7.0	%	N/A		N/A
Tier 1 capital (to average assets)		466,369		8.5	%		219,309		4.0	%	N/A		N/A
Cambridge Trust Company:
Total capital (to risk-weighted assets)	$	490,175		13.1	%	$	393,246		10.5	%	$	374,520		10.0	%
Tier 1 capital (to risk-weighted assets)		450,305		12.0	%		318,342		8.5	%		299,616		8.0	%
Common equity tier I capital (to risk-weighted assets)		450,305		12.0	%		262,164		7.0	%		243,438		6.5	%
Tier 1 capital (to average assets)		450,305		8.2	%		219,296		4.0	%		274,120		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	%