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DESCRIPTION OF BUSINESS (Details)	Sep. 30, 2025 investmentGroup
Accounting Policies [Abstract]
Number of investment groups	3

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- Definition

Number Of Investment Groups

+ References

No definition available.

+ Details

Name:	nly_NumberOfInvestmentGroups
Namespace Prefix:	nly_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

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- References

No definition available.

+ Details

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