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Summary of Significant Accounting Policies - Schedule of Properties (Details) - New Mountain Net Lease Corporation ft² in Thousands, $ in Thousands	Sep. 30, 2024 USD ($) ft²
Property, Plant and Equipment [Line Items]
Fair value	$ 124,880
NM NL Holdings LP / NM GP Holdco LLC
Property, Plant and Equipment [Line Items]
Fair value	$ 104,888
NM CLFX LP
Property, Plant and Equipment [Line Items]
Total square feet | ft²	423
Fair value	$ 10,031
NM YI, LLC
Property, Plant and Equipment [Line Items]
Total square feet | ft²	212
Fair value	$ 9,961

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Area of a real estate property.

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- Definition

Fair value portion of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2E
-Publisher FASB
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Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
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-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2003/role/exampleRef
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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 20
-Name Accounting Standards Codification
-Section 50
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