No definition available.

Name:	dcom_AssetsAndLiabilitiesMeasuredAtFairValueOnNonrecurringBasisAbstract
Namespace Prefix:	dcom_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount excluding accrued interest, of allowance for credit loss on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479344/326-20-45-1

+ Details

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

- Definition

Amortized cost excluding accrued interest, after allowance for credit loss, of financing receivable. Excludes net investment in lease.

+ References

+ Details

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

- Definition

Amount, excluding accrued interest, of credit loss expense (reversal of expense) on financing receivable. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

+ Details

Name:	us-gaap_FinancingReceivableExcludingAccruedInterestCreditLossExpenseReversal
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-10

+ Details

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

- Details

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

FAIR VALUE OF FINANCIAL INSTRUMENTS - Individually evaluated loans (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Abstract]
Individually evaluated loans outstanding balance, net of a valuation allowance	$ 10,747,046		$ 10,747,046		$ 10,701,685
Allowance for credit losses	77,812		77,812		71,743
Provision (recovery) for credit losses	5,585	$ 892	10,795	$ (2,756)
Fair Value, Nonrecurring [Member]
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Abstract]
Individually evaluated loans outstanding balance, net of a valuation allowance	2,300		2,300		7,300
Allowance for credit losses	1,500		1,500		1,000
Provision (recovery) for credit losses			807
Fair Value, Nonrecurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Abstract]
Individually evaluated loans	823		823		6,336
Reported Value Measurement [Member]
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Abstract]
Individually evaluated loans	10,746,223		10,746,223		10,695,349
Reported Value Measurement [Member] \| Fair Value, Nonrecurring [Member]
Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis [Abstract]
Individually evaluated loans	$ 823		$ 823		$ 6,336