DERIVATIVES AND HEDGING ACTIVITIES - Risk Participation and Credit Risk Related Contingent Features (Details)	3 Months Ended	9 Months Ended
Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($)
DERIVATIVES AND HEDGING ACTIVITIES
Risk Participation Agreements, Liabilities, Notional Value	$ 94,000,000.0		$ 94,000,000.0		$ 71,100,000
Credit Risk Related Contingent Features [Abstract]
Number of provisions breached	0	0	0	0

Represents the notional value, at balance sheet date, of risk participation agreements not designated as hedges of derivative liabilities.

No definition available.

Name:	dcom_RiskParticipationAgreementsLiabilitiesNotionalValue
Namespace Prefix:	dcom_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant