Fair Value Measurements - Recurring and Nonrecurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019
Fair Value \| Fair Value, Measurements, Recurring \| Interest-rate swaps
Liabilities, Fair Value Disclosure [Abstract]
Fair value of liabilities	$ 5,100	$ 625
Fair Value \| Fair Value, Measurements, Recurring \| Debt securities
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	582,303	504,788
Fair Value \| Fair Value, Measurements, Recurring \| Equity securities
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	746	467
Fair Value \| Fair Value, Measurements, Recurring \| FHLB Stock
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	1,905
Fair Value \| Fair Value, Measurements, Recurring \| Interest-rate swaps
Assets, Fair Value Disclosure [Abstract]
Fair value of assets		625
Fair Value \| Fair Value, Measurements, Recurring \| Interest-rate swaps \| Interest-rate swaps
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	2,286
Fair Value \| Fair Value, Measurements, Nonrecurring
Assets, Fair Value Disclosure [Abstract]
Impaired loans (collateral dependent)	18,733	1,268
Liabilities, Fair Value Disclosure [Abstract]
Specific allowance for collateral dependent impaired loans	$ 5,800	564
Letter of Credit
Liabilities, Fair Value Disclosure [Abstract]
Amortization period of estimated fair value on letters of credit	1 year
Fair Value, Measurements, Recurring \| Level 1 \| Interest-rate swaps
Liabilities, Fair Value Disclosure [Abstract]
Fair value of liabilities	$ 0	0
Fair Value, Measurements, Recurring \| Level 1 \| Debt securities
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Equity securities
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	746	467
Fair Value, Measurements, Recurring \| Level 1 \| FHLB Stock
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	0	0
Fair Value, Measurements, Recurring \| Level 1 \| Interest-rate swaps
Assets, Fair Value Disclosure [Abstract]
Fair value of assets		0
Fair Value, Measurements, Recurring \| Level 1 \| Interest-rate swaps \| Interest-rate swaps
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	0
Fair Value, Measurements, Recurring \| Level 2 \| Interest-rate swaps
Liabilities, Fair Value Disclosure [Abstract]
Fair value of liabilities	5,100	625
Fair Value, Measurements, Recurring \| Level 2 \| Debt securities
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	582,303	504,788
Fair Value, Measurements, Recurring \| Level 2 \| Equity securities
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	0	0
Fair Value, Measurements, Recurring \| Level 2 \| FHLB Stock
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	1,905	4,484
Fair Value, Measurements, Recurring \| Level 2 \| Interest-rate swaps
Assets, Fair Value Disclosure [Abstract]
Fair value of assets		625
Fair Value, Measurements, Recurring \| Level 2 \| Interest-rate swaps \| Interest-rate swaps
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	2,286
Fair Value, Measurements, Recurring \| Level 3 \| Interest-rate swaps
Liabilities, Fair Value Disclosure [Abstract]
Fair value of liabilities	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Debt securities
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Equity securities
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	0	0
Fair Value, Measurements, Recurring \| Level 3 \| FHLB Stock
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	0	0
Fair Value, Measurements, Recurring \| Level 3 \| Interest-rate swaps
Assets, Fair Value Disclosure [Abstract]
Fair value of assets		0
Fair Value, Measurements, Recurring \| Level 3 \| Interest-rate swaps \| Interest-rate swaps
Assets, Fair Value Disclosure [Abstract]
Fair value of assets	0
Fair Value, Measurements, Nonrecurring \| Level 1
Assets, Fair Value Disclosure [Abstract]
Impaired loans (collateral dependent)	0	0
Fair Value, Measurements, Nonrecurring \| Level 2
Assets, Fair Value Disclosure [Abstract]
Impaired loans (collateral dependent)	0	0
Fair Value, Measurements, Nonrecurring \| Level 3
Assets, Fair Value Disclosure [Abstract]
Impaired loans (collateral dependent)	$ 18,733	1,268
Valuation, Cost Approach \| Fair Value, Measurements, Recurring \| FHLB Stock
Assets, Fair Value Disclosure [Abstract]
Fair value of assets		$ 4,484

Estimated fair value, amortization period

No definition available.

Name:	ebtc_EstimatedFairValueAmortizationPeriod
Namespace Prefix:	ebtc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

For fair value measurement, the value of collateral dependent impaired loans.

+ References

No definition available.

+ Details

Name:	ebtc_ImpairedLoansCollateralDependentFairValueDisclosure
Namespace Prefix:	ebtc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Specific allowance for non recurring measured collateral dependent impaired loans.

+ References

No definition available.

+ Details

Name:	ebtc_ImpairedLoansCollateralDependentRelatedAllowance
Namespace Prefix:	ebtc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_AssetsFairValueDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

+ References

No definition available.

+ Details

Name:	us-gaap_FinancialLiabilitiesFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

Name:	us-gaap_LiabilitiesFairValueDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FairValueByMeasurementBasisAxis=us-gaap_EstimateOfFairValueFairValueDisclosureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByLiabilityClassAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_DebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_FederalHomeLoanBankCertificatesAndObligationsFHLBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByAssetClassAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsNonrecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LossContingenciesByNatureOfContingencyAxis=us-gaap_FinancialStandbyLetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_ValuationTechniqueAxis=us-gaap_CostApproachValuationTechniqueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: