Name:	dcom_HoldingsOfSecuritiesOfAnyOneIssuerGreaterThan10PercentOfStockholdersEquity
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Period Type:	instant

Threshold percentage which the entity uses for disclosure.

No definition available.

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Data Type:	dtr-types:percentItemType
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Period Type:	duration

The amount of transfers of securities held-to-maturity to securities available-for-sale.

No definition available.

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Data Type:	xbrli:monetaryItemType
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Represents unrealized losses are related to credit losses.

No definition available.

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Amount excluding accrued interest, of allowance for credit loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 1
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-URI https://asc.fasb.org//1943274/2147479130/326-30-45-1

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position without allowance for credit loss.

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 326
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-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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The aggregate fair value as of the balance sheet date of financial instruments and other positions owned by the entity including: (1) mortgages, mortgage-backed and asset backed securities; (2) US government and agency obligations; (3) state and municipal government obligations; (4) other sovereign government debt; (5) corporate obligations; (6) corporate equities; (7) principal investments; (8) derivative contracts; and (9) physical commodities. Includes both pledged and unpledged holdings.

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Balance Type:	debit
Period Type:	instant

Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
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-Subparagraph (SX 210.5-03.7(b))
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-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

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Balance Type:	credit
Period Type:	duration

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.