Shareholders' Equity (Tables)

9 Months Ended

Sep. 30, 2023

Equity [Abstract]

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

As of September 30, 2023 and December 31, 2022, 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 September 30, 2023
Cambridge Bancorp:
Total capital (to risk-weighted assets)	$	518,398		14.2	%	$	383,672		10.5	%	N/A		N/A
Tier 1 capital (to risk-weighted assets)		478,273		13.1	%		310,591		8.5	%	N/A		N/A
Common equity tier I capital (to risk-weighted assets)		478,273		13.1	%		255,781		7.0	%	N/A		N/A
Tier 1 capital (to average assets)		478,273		8.8	%		216,714		4.0	%	N/A		N/A
Cambridge Trust Company:
Total capital (to risk-weighted assets)	$	496,819		13.6	%	$	383,636		10.5	%	$	365,368		10.0	%
Tier 1 capital (to risk-weighted assets)		456,694		12.5	%		310,563		8.5	%		292,294		8.0	%
Common equity tier I capital (to risk-weighted assets)		456,694		12.5	%		255,757		7.0	%		237,489		6.5	%
Tier 1 capital (to average assets)		456,694		8.4	%		216,700		4.0	%		270,875		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, 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	%