Shareholders' Equity (Tables)

6 Months Ended

Jun. 30, 2021

Equity [Abstract]

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

As of June 30, 2021 and December 31, 2020, 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 June 30, 2021
Cambridge Bancorp:
Total capital (to risk-weighted assets)	$	401,412		13.9	%	$	303,775		10.5	%	N/A		N/A
Tier I capital (to risk-weighted assets)		365,434		12.6	%		245,913		8.5	%	N/A		N/A
Common equity tier I capital (to risk-weighted assets)		365,434		12.6	%		202,516		7.0	%	N/A		N/A
Tier I capital (to average assets)		365,434		8.7	%		167,450		4.0	%	N/A		N/A
Cambridge Trust Company:
Total capital (to risk-weighted assets)	$	396,759		13.7	%	$	303,746		10.5	%	$	289,282		10.0	%
Tier I capital (to risk-weighted assets)		360,781		12.5	%		245,890		8.5	%		231,426		8.0	%
Common equity tier I capital (to risk-weighted assets)		360,781		12.5	%		202,497		7.0	%		188,033		6.5	%
Tier I capital (to average assets)		360,781		8.6	%		167,439		4.0	%		209,299		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 I 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 I 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 I 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 I capital (to average assets)		342,229		8.8	%		154,999		4.0	%		193,748		5.0	%