NATURE OF OPERATIONS (Details)	3 Months Ended
Mar. 31, 2017 RetailBranch
NATURE OF OPERATIONS [Abstract]
Number of retail banking offices	27

The number of full service retail banking offices at period end.

No definition available.

Name:	dcom_NumberOfRetailOffices
Namespace Prefix:	dcom_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration