XML 108 R84.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Distributions - Costs of Investments for Tax Purposes (Details) - USD ($) $ in Thousands | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022
--- | --- | --- | ---
Income Tax Disclosure [Abstract] |  |  |
Tax cost | $ 2,978,976 | $ 2,927,312 | $ 3,209,491
Gross unrealized appreciation on investments | 562,558 | 466,794 | 438,214
Gross unrealized depreciation on investments | (437,010) | (366,284) | (409,919)
Total investments at fair value | $ 3,104,524 | $ 3,027,822 | $ 3,237,786

X
- Definition Tax Basis Of Investments, Fair Value For Income Tax Purposes + References No definition available. + Details
Name: | nmfc_TaxBasisOfInvestmentsFairValueForIncomeTaxPurposes
Namespace Prefix: | nmfc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_IncomeTaxDisclosureAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of cost of investment for federal income tax purpose. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-03(h)(2)(iv)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3 + Details
Name: | us-gaap_TaxBasisOfInvestmentsCostForIncomeTaxPurposes
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of cumulative increase in investment from unrealized gain when value exceeds cost for federal income tax purpose. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-03(h)(2)(i)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3 + Details
Name: | us-gaap_TaxBasisOfInvestmentsGrossUnrealizedAppreciation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of cumulative decrease in investment from unrealized loss when cost for federal income tax purpose exceeds value. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 946 -SubTopic 10 -Name Accounting Standards Codification -Section S99 -Paragraph 3 -Subparagraph (SX 210.6-03(h)(2)(ii)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479886/946-10-S99-3 + Details
Name: | us-gaap_TaxBasisOfInvestmentsGrossUnrealizedDepreciation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant