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DERIVATIVE INSTRUMENTS - Summary of Characteristics of TBA Derivatives (Details) - TBA derivatives - Purchase contracts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Derivative [Line Items]
Notional	$ 20,133,000	$ 19,635,000
Implied Cost Basis	20,289,856	20,277,088
Implied Market Value	20,338,633	20,373,197
Net Carrying Value	$ 48,777	$ 96,109

X

- Definition

TBA Securities cost.

+ References

No definition available.

+ Details

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Balance Type:	debit
Period Type:	duration

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- Definition

TBA Securities fair market value.

+ References

No definition available.

+ Details

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Namespace Prefix:	nly_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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X

- Definition

Nominal or face amount used to calculate payments on the derivative asset.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5580258-113959

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5579245-113959

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X

- Definition

Fair value of the assets less the liabilities of a derivative or group of derivatives.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=123594938&loc=d3e13433-108611

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- 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.

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