XML 77 R63.htm IDEA: XBRL DOCUMENT
v3.22.4

Borrowings - Summary of SBA-guaranteed Debentures (Details) $ in Thousands | Dec. 31, 2022 USD ($)
--- | ---
Debt Instrument [Line Items] |
Debenture Amount | $ 300,000
$37,500 SBA-guaranteed Debentures, Issued March 2015 | SBIC I |
Debt Instrument [Line Items] |
Debenture Amount | $ 37,500
$37,500 SBA-guaranteed Debentures, Issued March 2015 | SBIC I | SBA-guaranteed debentures |
Debt Instrument [Line Items] |
Interest Rate | 2.517%
SBA Annual Charge | 0.355%
$37,50 SBA-guaranteed Debentures, Issued September 2015 | SBIC I |
Debt Instrument [Line Items] |
Debenture Amount | $ 37,500
$37,50 SBA-guaranteed Debentures, Issued September 2015 | SBIC I | SBA-guaranteed debentures |
Debt Instrument [Line Items] |
Interest Rate | 2.829%
SBA Annual Charge | 0.355%
$28,795 SBA-guaranteed Debentures, Issued September 2015 | SBIC I |
Debt Instrument [Line Items] |
Debenture Amount | $ 28,795
$28,795 SBA-guaranteed Debentures, Issued September 2015 | SBIC I | SBA-guaranteed debentures |
Debt Instrument [Line Items] |
Interest Rate | 2.829%
SBA Annual Charge | 0.742%
$13,950 SBA-guaranteed debentures, Issued March 2016 | SBIC I |
Debt Instrument [Line Items] |
Debenture Amount | $ 13,950
$13,950 SBA-guaranteed debentures, Issued March 2016 | SBIC I | SBA-guaranteed debentures |
Debt Instrument [Line Items] |
Interest Rate | 2.507%
SBA Annual Charge | 0.742%
$4,000 SBA-guaranteed debentures, Issued September 2016 | SBIC I |
Debt Instrument [Line Items] |
Debenture Amount | $ 4,000
$4,000 SBA-guaranteed debentures, Issued September 2016 | SBIC I | SBA-guaranteed debentures |
Debt Instrument [Line Items] |
Interest Rate | 2.051%
SBA Annual Charge | 0.742%
$13,000 SBA-guaranteed debentures, Issued September 2017 | SBIC I |
Debt Instrument [Line Items] |
Debenture Amount | $ 13,000
$13,000 SBA-guaranteed debentures, Issued September 2017 | SBIC I | SBA-guaranteed debentures |
Debt Instrument [Line Items] |
Interest Rate | 2.518%
SBA Annual Charge | 0.742%
$15,255 SBA-guaranteed debentures, Issued March 2018 | SBIC I |
Debt Instrument [Line Items] |
Debenture Amount | $ 15,255
$15,255 SBA-guaranteed debentures, Issued March 2018 | SBIC I | SBA-guaranteed debentures |
Debt Instrument [Line Items] |
Interest Rate | 3.187%
SBA Annual Charge | 0.742%
$15,000 SBA-guaranteed debentures, Issued September 2018 | SBIC II |
Debt Instrument [Line Items] |
Debenture Amount | $ 15,000
$15,000 SBA-guaranteed debentures, Issued September 2018 | SBIC II | SBA-guaranteed debentures |
Debt Instrument [Line Items] |
Interest Rate | 3.548%
SBA Annual Charge | 0.222%
$19,000 SBA-guaranteed debentures, Issued September 2019 | SBIC II |
Debt Instrument [Line Items] |
Debenture Amount | $ 19,000
$19,000 SBA-guaranteed debentures, Issued September 2019 | SBIC II | SBA-guaranteed debentures |
Debt Instrument [Line Items] |
Interest Rate | 2.283%
SBA Annual Charge | 0.222%
$41,000 SBA-guaranteed debentures, Issued March 2020 | SBIC II |
Debt Instrument [Line Items] |
Debenture Amount | $ 41,000
$41,000 SBA-guaranteed debentures, Issued March 2020 | SBIC II | SBA-guaranteed debentures |
Debt Instrument [Line Items] |
Interest Rate | 2.078%
SBA Annual Charge | 0.222%
$24,000 SBA-guaranteed debentures, Issued March 2020 | SBIC II |
Debt Instrument [Line Items] |
Debenture Amount | $ 24,000
$24,000 SBA-guaranteed debentures, Issued March 2020 | SBIC II | SBA-guaranteed debentures |
Debt Instrument [Line Items] |
Interest Rate | 2.078%
SBA Annual Charge | 0.275%
$50,000 SBA-guaranteed debentures, Issued September 2020 | SBIC II |
Debt Instrument [Line Items] |
Debenture Amount | $ 51,000
$50,000 SBA-guaranteed debentures, Issued September 2020 | SBIC II | SBA-guaranteed debentures |
Debt Instrument [Line Items] |
Interest Rate | 1.034%
SBA Annual Charge | 0.275%

X
- Definition Debt Instrument, Annual Charge, Percentage + References No definition available. + Details
Name: | nmfc_DebtInstrumentAnnualChargePercentage
Namespace Prefix: | nmfc_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Face (par) amount of debt instrument at time of issuance. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 1B -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI https://asc.fasb.org/extlink&oid=124435984&loc=d3e28551-108399 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 55 -Paragraph 8 -URI https://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 50 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=124429444&loc=SL124452920-239629 Reference 5: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 55 -Paragraph 69C -URI https://asc.fasb.org/extlink&oid=123466577&loc=SL123495737-112612 Reference 6: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 55 -Paragraph 69B -URI https://asc.fasb.org/extlink&oid=123466577&loc=SL123495735-112612 + Details
Name: | us-gaap_DebtInstrumentFaceAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 470 -SubTopic 20 -Section 50 -Paragraph 6 -Subparagraph (a) -URI https://asc.fasb.org/extlink&oid=123466204&loc=SL6036836-161870 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 2 -URI https://asc.fasb.org/extlink&oid=124435984&loc=d3e28551-108399 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 50 -Paragraph 1 -URI https://asc.fasb.org/extlink&oid=124429444&loc=SL124452920-239629 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
Name: | us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
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_DebtInstrumentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nmfc_USD37500SBAGuaranteedDebenturesIssuedMarch2015Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=nmfc_NewMountainFinanceSBICLPMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=nmfc_GuaranteedDebtMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nmfc_USD3750SBAGuaranteedDebenturesIssuedSeptember2015Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nmfc_USD28795SBAGuaranteedDebenturesIssuedSeptember2015Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nmfc_USD13950SBAGuaranteedDebenturesIssuedMarch2016Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nmfc_USD4000SBAGuaranteedDebenturesIssuedSeptember2016Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nmfc_USD13000SBAGuaranteedDebenturesIssuedSeptember2017Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nmfc_USD15255SBAGuaranteedDebenturesIssuedMarch2018Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nmfc_USD15000SBAGuaranteedDebenturesIssuedSeptember2018Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=nmfc_NewMountainFinanceSBICIILPMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nmfc_USD19000SBAGuaranteedDebenturesIssuedSeptember2019Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nmfc_USD41000SBAGuaranteedDebenturesIssuedMarch2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nmfc_USD24000SBAGuaranteedDebenturesIssuedMarch2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DebtInstrumentAxis=nmfc_USD50000SBAGuaranteedDebenturesIssuedSeptember2020Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |