XML 61 R49.htm IDEA: XBRL DOCUMENT
v3.21.1

SECURITIES - Narrative (Details) - USD ($) | 3 Months Ended
--- | ---
Mar. 31, 2021 | Mar. 31, 2020
Debt Securities, Available-for-sale [Line Items] |  |
Residential Investment securities sold, carrying value | $ 3,000,000,000.0 | $ 41,900,000,000
Commercial Mortgage Backed Securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Impairment, available-for-sale debt security | $ 400,000 | $ 0

X
- Definition Carrying value of mortgage backed securities sold during period. + References No definition available. + Details
Name: | nly_MortgageBackedSecuritiesSoldCarryingValue
Namespace Prefix: | nly_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of other-than-temporary impairment (OTTI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), recognized in earnings and other comprehensive loss (OCI). + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 8A -URI http://asc.fasb.org/extlink&oid=121553693&loc=SL6284422-111562 + Details
Name: | us-gaap_OtherThanTemporaryImpairmentLossDebtSecuritiesAvailableForSale
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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

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