RECENTLY ISSUED ACCOUNTING STANDARDS (Details)	Dec. 31, 2018
ASU 2016-02 [Member] \| Maximum [Member]
Leases [Abstract]
Percentage of increase in total assets due to adoption	1.00%

Percentage of increases in assets and did not have a significant impact on the Consolidated Statement of Income or Consolidated Statement of Cash Flows due to adoption of new accounting standards.

No definition available.

Name:	dcom_PercentageOfIncreaseInTotalAssetsDueToAdoptionOfNewAccountingStandards
Namespace Prefix:	dcom_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant