PREMISES HELD FOR SALE (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
PREMISES HELD FOR SALE [Abstract]
Premises held for sale	$ 8,799	$ 0
Aggregate purchase price under purchase and sale agreement	$ 80,000

Aggregate purchase price for premise held for sale under purchase and sale agreement. Sale expected to close in February 2016.

No definition available.

Name:	dcom_AggregatePurchasePriceUnderPurchaseAndSaleAgreement
Namespace Prefix:	dcom_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant