XML 69 R59.htm IDEA: XBRL DOCUMENT
v3.21.1

LOANS HELD FOR INVESTMENT, NET - Allowance by Class of Loan (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | ---
Mar. 31, 2021 | Mar. 31, 2020 | Dec. 31, 2020 | Mar. 31, 2021 | Dec. 31, 2020
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | $ 41,461 | $ 28,441 | $ 28,441 |  |
PCD Day 1 | 52,284 |  |  |  |
Provision (credit) for credit losses | 12,649 | 8,012 |  |  |
Charge-offs | (4,275) | (6) |  |  |
Recoveries |  | 16 |  |  |
Ending balance | 98,200 | 36,463 | 41,461 |  |
Non-accrual with No Allowance for Credit Loss |  |  |  | $ 8,396 |
Non-accrual with Allowance |  |  |  | 27,153 |
Reserve | 10,918 |  |  |  |
Interest income on non-accrual loans | 0 |  |  |  |
CECL | 3,900 |  |  |  |
Non-PCD | 20,300 |  |  |  |
Impact of improvement in forecasted macroeconomic conditions |  |  | (7,600) |  |
Allowance for loan losses: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | $ 6,474
Collectively evaluated for impairment |  |  |  |  | 34,987
Total ending allowance balance | 98,200 | 36,463 | 28,441 | 98,200 | 41,461
Loans: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 17,069
Collectively evaluated for impairment |  |  |  |  | 5,604,975
Total ending loans balance |  |  |  |  | 5,622,044
Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | (3,919) |  |  |  |
Ending balance |  |  | (3,919) |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | (3,919) |  | (3,919) |  | (3,919)
Cumulative Effect, Period of Adoption, Adjusted Balance |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 37,542 |  |  |  |
Ending balance |  |  | 37,542 |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | 37,542 |  | 37,542 |  | 37,542
One-to-four family residential and cooperative/condominium apartment |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Non-accrual with Allowance |  |  |  | 5,384 |
Reserve | 134 |  |  |  |
Multifamily residential and residential mixed-use |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Non-accrual with No Allowance for Credit Loss |  |  |  | 4,844 |
Commercial real estate ("CRE") |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Non-accrual with No Allowance for Credit Loss |  |  |  | 3,552 |
Non-accrual with Allowance |  |  |  | 7,043 |
Reserve | 2,786 |  |  |  |
Acquisition, development, and construction ("ADC") |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Non-accrual with Allowance |  |  |  | 104 |
Reserve | 59 |  |  |  |
Real estate |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 28,712 | 15,555 | 15,555 |  |
PCD Day 1 | 28,753 |  |  |  |
Provision (credit) for credit losses | 9,059 | 7,372 |  |  |
Charge-offs | (258) | (6) |  |  |
Recoveries |  | 14 |  |  |
Ending balance | 64,290 | 22,935 | 28,712 |  |
Allowance for loan losses: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 0
Collectively evaluated for impairment |  |  |  |  | 28,712
Total ending allowance balance | 64,290 | 22,935 | 15,555 | 64,290 | 28,712
Loans: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 4,567
Collectively evaluated for impairment |  |  |  |  | 4,973,628
Total ending loans balance |  |  |  |  | 4,978,195
Real estate | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | (1,976) |  |  |  |
Ending balance |  |  | (1,976) |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | (1,976) |  | (1,976) |  | (1,976)
Real estate | Cumulative Effect, Period of Adoption, Adjusted Balance |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 26,736 |  |  |  |
Ending balance |  |  | 26,736 |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | 26,736 |  | 26,736 |  | 26,736
Real estate | One-to-four family residential and cooperative/condominium apartment |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 644 | 269 | 269 |  |
PCD Day 1 | 2,220 |  |  |  |
Provision (credit) for credit losses | 1,235 | 376 |  |  |
Charge-offs | (14) | 0 |  |  |
Recoveries |  | 0 |  |  |
Ending balance | 5,133 | 645 | 644 |  |
Allowance for loan losses: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 0
Collectively evaluated for impairment |  |  |  |  | 644
Total ending allowance balance | 5,133 | 645 | 269 | 5,133 | 644
Loans: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 0
Collectively evaluated for impairment |  |  |  |  | 184,989
Total ending loans balance |  |  |  |  | 184,989
Real estate | One-to-four family residential and cooperative/condominium apartment | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 1,048 |  |  |  |
Ending balance |  |  | 1,048 |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | 1,048 |  | 1,048 |  | 1,048
Real estate | One-to-four family residential and cooperative/condominium apartment | Cumulative Effect, Period of Adoption, Adjusted Balance |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 1,692 |  |  |  |
Ending balance |  |  | 1,692 |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | 1,692 |  | 1,692 |  | 1,692
Real estate | Multifamily residential and residential mixed-use |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 17,016 | 10,142 | 10,142 |  |
PCD Day 1 | 3,292 |  |  |  |
Provision (credit) for credit losses | (1,397) | 4,127 |  |  |
Charge-offs | (236) | 0 |  |  |
Recoveries |  | 14 |  |  |
Ending balance | 10,421 | 14,283 | 17,016 |  |
Allowance for loan losses: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 0
Collectively evaluated for impairment |  |  |  |  | 17,016
Total ending allowance balance | 10,421 | 14,283 | 10,142 | 10,421 | 17,016
Loans: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 1,863
Collectively evaluated for impairment |  |  |  |  | 2,756,880
Total ending loans balance |  |  |  |  | 2,758,743
Real estate | Multifamily residential and residential mixed-use | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | (8,254) |  |  |  |
Ending balance |  |  | (8,254) |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | (8,254) |  | (8,254) |  | (8,254)
Real estate | Multifamily residential and residential mixed-use | Cumulative Effect, Period of Adoption, Adjusted Balance |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 8,762 |  |  |  |
Ending balance |  |  | 8,762 |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | 8,762 |  | 8,762 |  | 8,762
Real estate | Commercial real estate ("CRE") |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 9,059 | 3,900 | 3,900 |  |
PCD Day 1 | 23,124 |  |  |  |
Provision (credit) for credit losses | 7,813 | 2,442 |  |  |
Charge-offs | (8) | (6) |  |  |
Recoveries |  | 0 |  |  |
Ending balance | 44,837 | 6,336 | 9,059 |  |
Allowance for loan losses: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 0
Collectively evaluated for impairment |  |  |  |  | 9,059
Total ending allowance balance | 44,837 | 6,336 | 3,900 | 44,837 | 9,059
Loans: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 2,704
Collectively evaluated for impairment |  |  |  |  | 1,875,463
Total ending loans balance |  |  |  |  | 1,878,167
Real estate | Commercial real estate ("CRE") | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 4,849 |  |  |  |
Ending balance |  |  | 4,849 |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | 4,849 |  | 4,849 |  | 4,849
Real estate | Commercial real estate ("CRE") | Cumulative Effect, Period of Adoption, Adjusted Balance |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 13,908 |  |  |  |
Ending balance |  |  | 13,908 |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | 13,908 |  | 13,908 |  | 13,908
Real estate | Acquisition, development, and construction ("ADC") |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 1,993 | 1,244 | 1,244 |  |
PCD Day 1 | 117 |  |  |  |
Provision (credit) for credit losses | 1,408 | 427 |  |  |
Charge-offs |  | 0 |  |  |
Recoveries |  | 0 |  |  |
Ending balance | 3,899 | 1,671 | 1,993 |  |
Allowance for loan losses: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 0
Collectively evaluated for impairment |  |  |  |  | 1,993
Total ending allowance balance | 3,899 | 1,671 | 1,244 | 3,899 | 1,993
Loans: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 0
Collectively evaluated for impairment |  |  |  |  | 156,296
Total ending loans balance |  |  |  |  | 156,296
Real estate | Acquisition, development, and construction ("ADC") | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 381 |  |  |  |
Ending balance |  |  | 381 |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | 381 |  | 381 |  | 381
Real estate | Acquisition, development, and construction ("ADC") | Cumulative Effect, Period of Adoption, Adjusted Balance |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 2,374 |  |  |  |
Ending balance |  |  | 2,374 |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | 2,374 |  | 2,374 |  | 2,374
Commercial and industrial ("C&I") |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 12,737 | 12,870 | 12,870 |  |
Provision (credit) for credit losses |  | 641 |  |  |
Charge-offs |  | 0 |  |  |
Recoveries |  | 2 |  |  |
Ending balance |  | 13,513 | 12,737 |  |
Allowance for loan losses: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 6,474
Collectively evaluated for impairment |  |  |  |  | 6,263
Total ending allowance balance | 12,737 | 13,513 | 12,737 |  | 12,737
Loans: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 12,502
Collectively evaluated for impairment |  |  |  |  | 629,031
Total ending loans balance |  |  |  |  | 641,533
Commercial and industrial ("C&I"), including SBA and PPP loans |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 12,737 |  |  |  |
PCD Day 1 | 23,374 |  |  |  |
Provision (credit) for credit losses | 3,219 |  |  |  |
Charge-offs | (4,017) |  |  |  |
Ending balance | 33,378 |  | 12,737 |  |
Non-accrual with Allowance |  |  |  | 14,523 |
Reserve | 7,881 |  |  |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | 33,378 |  | 12,737 | 33,378 | 12,737
Commercial and industrial ("C&I"), including SBA and PPP loans | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | (1,935) |  |  |  |
Ending balance |  |  | (1,935) |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | (1,935) |  | (1,935) |  | (1,935)
Commercial and industrial ("C&I"), including SBA and PPP loans | Cumulative Effect, Period of Adoption, Adjusted Balance |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 10,802 |  |  |  |
Ending balance |  |  | 10,802 |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | 10,802 |  | 10,802 |  | 10,802
Other loans |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 12 | 16 | 16 |  |
PCD Day 1 | 157 |  |  |  |
Provision (credit) for credit losses | 371 | (1) |  |  |
Charge-offs |  | 0 |  |  |
Recoveries |  | 0 |  |  |
Ending balance | 532 | 15 | 12 |  |
Non-accrual with Allowance |  |  |  | 99 |
Reserve | 58 |  |  |  |
Allowance for loan losses: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 0
Collectively evaluated for impairment |  |  |  |  | 12
Total ending allowance balance | 532 | $ 15 | 16 | $ 532 | 12
Loans: |  |  |  |  |
Individually evaluated for impairment |  |  |  |  | 0
Collectively evaluated for impairment |  |  |  |  | 2,316
Total ending loans balance |  |  |  |  | 2,316
Other loans | Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | (8) |  |  |  |
Ending balance |  |  | (8) |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | (8) |  | (8) |  | (8)
Other loans | Cumulative Effect, Period of Adoption, Adjusted Balance |  |  |  |  |
Allowance for loan losses [Roll Forward] |  |  |  |  |
Beginning balance | 4 |  |  |  |
Ending balance |  |  | 4 |  |
Allowance for loan losses: |  |  |  |  |
Total ending allowance balance | $ 4 |  | $ 4 |  | $ 4

X
- Definition The amount expected credit losses with one year. + References No definition available. + Details
Name: | dcom_CurrentExpectedCreditLosses
Namespace Prefix: | dcom_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition NA + References No definition available. + Details
Name: | dcom_EndingAllowanceBalanceAbstract
Namespace Prefix: | dcom_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount at purchase price of financing receivable purchased without credit deterioration. + References No definition available. + Details
Name: | dcom_FinancingReceivablePurchasedWithoutCreditDeteriorationAmountAtPurchasePrice
Namespace Prefix: | dcom_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Represents improvement in forecasted macroeconomic conditions. + References No definition available. + Details
Name: | dcom_ImprovementInForecastedMacroeconomicConditions
Namespace Prefix: | dcom_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition NA + References No definition available. + Details
Name: | dcom_LoanAbstract
Namespace Prefix: | dcom_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(7)(2)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=121599878&loc=SL82895884-210446 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLosses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of increase in allowance for credit loss on financing receivable from recovery. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922352-210448 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(4) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesRecovery
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of writeoff of financing receivable, charged against allowance for credit loss. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922352-210448 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesWriteOffs
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The balance of financing receivables that were collectively evaluated for impairment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The balance of financing receivables that were individually evaluated for impairment. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of interest income on financing receivable on nonaccrual status. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 16 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919258-210447 + Details
Name: | us-gaap_FinancingReceivableNonaccrualInterestIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of financing receivable on nonaccrual status with no allowance for credit loss. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 16 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919258-210447 + Details
Name: | us-gaap_FinancingReceivableNonaccrualNoAllowance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount at purchase price of financing receivable purchased with credit deterioration. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 19 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919265-210447 + Details
Name: | us-gaap_FinancingReceivablePurchasedWithCreditDeteriorationAmountAtPurchasePrice
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of financing receivable on nonaccrual status. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 7 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5111-111524 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 16 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919258-210447 + Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentNonaccrualStatus
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5074-111524 + Details
Name: | us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953423-111524 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.11) -URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585 + Details
Name: | us-gaap_ProvisionForLoanLeaseAndOtherLosses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of credit loss expense (reversal of expense) for financing receivable. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919249-210447 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(11)) -URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260 + Details
Name: | us-gaap_ProvisionForLoanLossesExpensed
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | srt_CumulativeEffectPeriodOfAdoptionAxis=srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_CumulativeEffectPeriodOfAdoptionAxis=srt_CumulativeEffectPeriodOfAdoptionAdjustedBalanceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=dcom_OneToFourFamilyResidentialAndCooperativeUnitAllowanceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=dcom_MultifamilyResidentialAndResidentialMixedUseAllowanceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=dcom_CommercialRealEstateLoansAndMixedUseCommercialRealEstateAllowanceMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=dcom_AcquisitionDevelopmentAndConstructionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=dcom_RealEstatePortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=dcom_CommercialAndIndustrialPortfolioSegmentIncludingSbaAndPppMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |