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LEASES - Narrative (Details) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2021 USD ($) lease item | Feb. 01, 2021 USD ($)
Lessee, Lease, Description [Line Items] |  |
Operating lease assets |  | $ 45.6
Operating lease liabilities |  | $ 45.3
Number of branches combined to other locations | item | 3 |
Corporate headquarters office space lease |  |
Lessee, Lease, Description [Line Items] |  |
Decrease in operating lease liability | $ 11.6 |
Early termination fee | $ 12.0 |
Number of leases terminated | lease | 1 |
Branch office space lease |  |
Lessee, Lease, Description [Line Items] |  |
Decrease in operating lease liability | $ 3.7 |
Early termination fee | $ 4.0 |
Number of leases terminated | lease | 3 |

X
- Definition Amount of operating lease assets acquired at the acquisition date. + References No definition available. + Details
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Namespace Prefix: | dcom_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of operating lease liabilities assumed in business combination. + References No definition available. + Details
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Namespace Prefix: | dcom_
Data Type: | xbrli:monetaryItemType
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X
- Definition The number of branches that is combined to other locations. + References No definition available. + Details
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Namespace Prefix: | dcom_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of leases terminated. + References No definition available. + Details
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Namespace Prefix: | dcom_
Data Type: | xbrli:integerItemType
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Period Type: | duration

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- Definition Amount of early termination fees. + References No definition available. + Details
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Namespace Prefix: | dcom_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- Definition Amount of increase (decrease) in obligation for operating lease. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (g)(1) -URI http://asc.fasb.org/extlink&oid=123408670&loc=SL77918686-209980 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585 + Details
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X
- Definition 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. + References No definition available. + Details
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X
- Details
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Namespace Prefix: |
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Balance Type: |
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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |