XML 129 R79.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

REAL ESTATE - Additional Information (Details) | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2019 USD ($) | Dec. 31, 2019 USD ($) property | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Real Estate Properties [Line Items] |  |  |  |
Real estate acquired in settlement of residential mortgage loans |  | $ 0 | $ 0 |
Number of commercial real estate acquired (property) | property |  | 0 |  |
Proceeds from sales of real estate | $ 0 | $ 24,955,000 |  | $ 0
Weighted average amortization period |  | 6 years |  |
MTGE Investment Corp |  |  |  |
Real Estate Properties [Line Items] |  |  |  |
Number of wholly owned real estate properties sold (property) | property |  | 2 |  |
Proceeds from sales of real estate |  | $ 25,200,000 |  |
Gain on sale of wholly-owned triple net leased properties |  | 7,500,000 |  |
General and Administrative Expense |  |  |  |
Real Estate Properties [Line Items] |  |  |  |
Depreciation expense |  | $ 23,700,000 | $ 18,100,000 |

X
- Definition Number Of Real Estate Properties Purchased + References No definition available. + Details
Name: | nly_NumberOfRealEstatePropertiesPurchased
Namespace Prefix: | nly_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number Of Real Estate Properties Sold + References No definition available. + Details
Name: | nly_NumberOfRealEstatePropertiesSold
Namespace Prefix: | nly_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Weighted Average Amortization Period + References No definition available. + Details
Name: | nly_WeightedAverageAmortizationPeriod
Namespace Prefix: | nly_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585 + Details
Name: | us-gaap_Depreciation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The net gain (loss) resulting from sales and other disposals of real estate owned for investment purposes. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(b)(9)(a)) -URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(b)(7)(c)) -URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227 Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(14)(d)) -URI http://asc.fasb.org/extlink&oid=114873765&loc=SL114874048-224260 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(3)(a)) -URI http://asc.fasb.org/extlink&oid=114873790&loc=SL114874131-224263 + Details
Name: | us-gaap_GainsLossesOnSalesOfInvestmentRealEstate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Cash received for the sale of real estate that is not part of an investing activity during the current period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3179-108585 + Details
Name: | us-gaap_ProceedsFromSaleOfRealEstate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Carrying amount as of the balance sheet date of land and buildings obtained through foreclosure proceedings or defeasance in full or partial satisfaction of a debt arrangement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5162-111524 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4437-111522 + Details
Name: | us-gaap_RealEstateAcquiredThroughForeclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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_RealEstatePropertiesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | nly_AssetAcquisitionsAxis=nly_MTGEInvestmentCorpMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=us-gaap_GeneralAndAdministrativeExpenseMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |