XML 79 R69.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Impact of Recent Accounting Pronouncements - Additional Information (Detail) - USD ($) $ in Thousands | 6 Months Ended | 12 Months Ended
--- | --- | ---
Jun. 30, 2018 | Dec. 31, 2017
Significant Accounting Policies [Line Items] |  |
Federal corporate income tax rate | 21.00% | 35.00%
ASU 2018-02 | Retained Earnings |  |
Significant Accounting Policies [Line Items] |  |
Effect of adopting | $ 2,546 |
ASU 2018-02 | Accumulated Other Comprehensive Loss |  |
Significant Accounting Policies [Line Items] |  |
Effect of adopting | $ (2,546) |

X
- Definition Effects of New Accounting Pronouncement or Change in Accounting Principle + References No definition available. + Details
Name: | nyb_EffectsOfNewAccountingPronouncementOrChangeInAccountingPrinciple
Namespace Prefix: | nyb_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Significant Accounting Policies [Line Items] + References No definition available. + Details
Name: | nyb_SignificantAccountingPoliciesLineItems
Namespace Prefix: | nyb_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of domestic federal statutory tax rate applicable to pretax income (loss). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 6.I) -URI http://asc.fasb.org/extlink&oid=34349781&loc=d3e330036-122817 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32687-109319 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32698-109319 + Details
Name: | us-gaap_EffectiveIncomeTaxRateReconciliationAtFederalStatutoryIncomeTaxRate
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_AdjustmentsForNewAccountingPronouncementsAxis=nyb_AccountingStandardsUpdate201802Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_RetainedEarningsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementEquityComponentsAxis=us-gaap_AccumulatedOtherComprehensiveIncomeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |