XML 129 R114.htm IDEA: XBRL DOCUMENT
v3.20.4

Employee Benefits - Fair Value Measurements of Investments Held by Retirement Plan (Parenthetical) (Detail) | Dec. 31, 2020 Stock Fund
--- | ---
Large-Cap Value | Minimum | Common/Collective Trusts - Equity |
Defined Benefit Plan Disclosure [Line Items] |
Number of stocks held | 60
Large-Cap Value | Maximum | Common/Collective Trusts - Equity |
Defined Benefit Plan Disclosure [Line Items] |
Number of stocks held | 70
Small-Cap Core | Equity Funds |
Defined Benefit Plan Disclosure [Line Items] |
Mutual fund investment in marketable securities with percentage of market capitalization | 10.00%
International Equity | Minimum | Equity Funds |
Defined Benefit Plan Disclosure [Line Items] |
Percentage of investments | 80.00%
U.S. Core | Fixed Income Funds |
Defined Benefit Plan Disclosure [Line Items] |
Number of mutual funds | Fund | 3
U.S. Core | Fixed Income Funds | Mortgage-backed Securities |
Defined Benefit Plan Disclosure [Line Items] |
Percentage of investments | 50.00%
U.S. Core | Minimum | Fixed Income Funds | Fixed Income Securities |
Defined Benefit Plan Disclosure [Line Items] |
Percentage of investments | 80.00%

X
- Definition Mutual fund investment in marketable securities with percentage of market capitalization. + References No definition available. + Details
Name: | nycb_MutualFundInvestmentInMarketableSecuritiesWithPercentageOfMarketCapitalization
Namespace Prefix: | nycb_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of mutual funds. + References No definition available. + Details
Name: | nycb_NumberOfMutualFunds
Namespace Prefix: | nycb_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Number of Stocks + References No definition available. + Details
Name: | nycb_NumberofStocks
Namespace Prefix: | nycb_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

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
Name: | us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of investment to total investment within defined benefit plan asset category. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(ii) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=118257860&loc=d3e4179-114921 + Details
Name: | us-gaap_DefinedBenefitPlanPlanAssetsInvestmentWithinPlanAssetCategoryPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=nycb_LargeCapValueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=nycb_CommonCollectiveTrustsEquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=nycb_SmallCapCoreMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_EquityFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=nycb_InternationalEquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentSecondaryCategorizationAxis=nycb_UnitedStatesCoreMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_FixedIncomeFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_MortgageBackedSecuritiesIssuedByUSGovernmentSponsoredEnterprisesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentAxis=us-gaap_FixedIncomeSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |