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INVESTMENTS - Schedule of Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation (Details)	9 Months Ended
	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value beginning of period	$ 2,244,908,000	$ 2,237,531,000
New investments	545,609,000	331,922,000
Investment restructuring	0	(22,249,000)
Transfers into Level 3	5,989,000
Transfers out of Level 3	(26,625,000)
Transfers into (out of) Level 3, net		(12,039,000)
Proceeds from sales of investments / return of capital	(176,846,000)	(27,806,000)
Loan origination fees received	(9,579,000)	(5,759,000)
Principal repayments received	(260,940,000)	(334,936,000)
Fair value end of period	2,371,108,000	2,177,434,000
Payment-in-kind interest / dividends
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 19,540,000	$ 13,968,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Total payment-in-kind interest income	Total payment-in-kind interest income
Accretion of loan premium / discount
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 248,000	$ 396,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and other financing fees	Interest and other financing fees
Accretion of deferred loan origination revenue
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 7,958,000	$ 8,042,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and other financing fees	Interest and other financing fees
Realized gain (loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ (25,821,000)	$ (26,433,000)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net realized gains (losses) on investments	Net realized gains (losses) on investments
Unrealized appreciation (depreciation)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 46,667,000	$ 14,797,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net unrealized appreciation (depreciation) on investments	Net unrealized appreciation (depreciation) on investments
Senior debt and 1st lien notes
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value beginning of period	$ 1,625,501,000	$ 1,593,797,000
New investments	459,219,000	291,822,000
Investment restructuring	424,000	(22,249,000)
Transfers into Level 3	0
Transfers out of Level 3	0
Transfers into (out of) Level 3, net		(5,770,000)
Proceeds from sales of investments / return of capital	(154,807,000)	(18,512,000)
Loan origination fees received	(7,929,000)	(5,463,000)
Principal repayments received	(208,334,000)	(271,403,000)
Fair value end of period	$ 1,738,067,000	1,559,820,000
Senior debt and 1st lien notes | Fair Value, Inputs, Level 3 | Transaction Price | Recent Transaction | Maximum
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Input	1.000		1.000
Senior debt and 1st lien notes | Payment-in-kind interest / dividends
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 6,831,000	$ 4,590,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Total payment-in-kind interest income	Total payment-in-kind interest income
Senior debt and 1st lien notes | Accretion of loan premium / discount
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 248,000	$ 313,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and other financing fees	Interest and other financing fees
Senior debt and 1st lien notes | Accretion of deferred loan origination revenue
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 7,200,000	$ 7,391,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and other financing fees	Interest and other financing fees
Senior debt and 1st lien notes | Realized gain (loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ (23,320,000)	$ (19,528,000)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net realized gains (losses) on investments	Net realized gains (losses) on investments
Senior debt and 1st lien notes | Unrealized appreciation (depreciation)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 33,034,000	$ 4,832,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net unrealized appreciation (depreciation) on investments	Net unrealized appreciation (depreciation) on investments
Subordinated debt and 2nd lien notes
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value beginning of period	$ 153,703,000	$ 223,798,000
New investments	60,065,000	28,741,000
Investment restructuring	(424,000)	0
Transfers into Level 3	5,989,000
Transfers out of Level 3	(10,159,000)
Transfers into (out of) Level 3, net		0
Proceeds from sales of investments / return of capital	0	(4,975,000)
Loan origination fees received	(1,650,000)	(296,000)
Principal repayments received	(20,684,000)	(62,050,000)
Fair value end of period	$ 191,672,000	187,305,000
Subordinated debt and 2nd lien notes | Fair Value, Inputs, Level 3 | Transaction Price | Recent Transaction
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Input	1.000		0.980
Subordinated debt and 2nd lien notes | Payment-in-kind interest / dividends
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 3,824,000	$ 1,313,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Total payment-in-kind interest income	Total payment-in-kind interest income
Subordinated debt and 2nd lien notes | Accretion of loan premium / discount
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 0	$ 83,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and other financing fees	Interest and other financing fees
Subordinated debt and 2nd lien notes | Accretion of deferred loan origination revenue
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 615,000	$ 651,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and other financing fees	Interest and other financing fees
Subordinated debt and 2nd lien notes | Realized gain (loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ (9,384,000)	$ (5,461,000)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net realized gains (losses) on investments	Net realized gains (losses) on investments
Subordinated debt and 2nd lien notes | Unrealized appreciation (depreciation)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 9,777,000	$ 5,501,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net unrealized appreciation (depreciation) on investments	Net unrealized appreciation (depreciation) on investments
Structured products
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value beginning of period	$ 48,664,000	$ 42,972,000
New investments	7,500,000	48,000
Investment restructuring	0	0
Transfers into Level 3	0
Transfers out of Level 3	(3,310,000)
Transfers into (out of) Level 3, net		0
Proceeds from sales of investments / return of capital	(1,998,000)	0
Loan origination fees received	0	0
Principal repayments received	(31,922,000)	(1,483,000)
Fair value end of period	17,777,000	45,682,000
Structured products | Fair Value, Inputs, Level 3 | Transaction Price | Recent Transaction
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Input			1.000
Structured products | Payment-in-kind interest / dividends
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 0	$ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Total payment-in-kind interest income	Total payment-in-kind interest income
Structured products | Accretion of loan premium / discount
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 0	$ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and other financing fees	Interest and other financing fees
Structured products | Accretion of deferred loan origination revenue
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 143,000	$ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and other financing fees	Interest and other financing fees
Structured products | Realized gain (loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ (1,560,000)	$ 42,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net realized gains (losses) on investments	Net realized gains (losses) on investments
Structured products | Unrealized appreciation (depreciation)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 260,000	$ 4,103,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net unrealized appreciation (depreciation) on investments	Net unrealized appreciation (depreciation) on investments
Equity shares
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value beginning of period	$ 408,475,000	$ 374,572,000
New investments	18,825,000	7,440,000
Investment restructuring	0	0
Transfers into Level 3	0
Transfers out of Level 3	(13,156,000)
Transfers into (out of) Level 3, net		(6,269,000)
Proceeds from sales of investments / return of capital	(15,265,000)	(4,238,000)
Loan origination fees received	0	0
Principal repayments received	0	0
Fair value end of period	$ 420,943,000	378,208,000
Equity shares | Fair Value, Inputs, Level 3 | Liabilities | Net Asset Approach
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Input			96,678,300
Equity shares | Fair Value, Inputs, Level 3 | Liabilities | Net Asset Approach | Maximum
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Input	117,088,000
Equity shares | Fair Value, Inputs, Level 3 | Transaction Price | Recent Transaction | Maximum
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Input	100.00		1,847.58
Equity shares | Payment-in-kind interest / dividends
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 8,885,000	$ 8,065,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Total payment-in-kind interest income	Total payment-in-kind interest income
Equity shares | Accretion of loan premium / discount
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 0	$ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and other financing fees	Interest and other financing fees
Equity shares | Accretion of deferred loan origination revenue
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 0	$ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and other financing fees	Interest and other financing fees
Equity shares | Realized gain (loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 5,976,000	$ (1,486,000)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net realized gains (losses) on investments	Net realized gains (losses) on investments
Equity shares | Unrealized appreciation (depreciation)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 7,203,000	$ 124,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net unrealized appreciation (depreciation) on investments	Net unrealized appreciation (depreciation) on investments
Equity warrants
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value beginning of period	$ 2,732,000	$ 2,392,000
New investments	0	0
Investment restructuring	0	0
Transfers into Level 3	0
Transfers out of Level 3	0
Transfers into (out of) Level 3, net		0
Proceeds from sales of investments / return of capital	0	0
Loan origination fees received	0	0
Principal repayments received	0	0
Fair value end of period	1,068,000	2,600,000
Equity warrants | Payment-in-kind interest / dividends
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 0	$ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Total payment-in-kind interest income	Total payment-in-kind interest income
Equity warrants | Accretion of loan premium / discount
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 0	$ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and other financing fees	Interest and other financing fees
Equity warrants | Accretion of deferred loan origination revenue
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 0	$ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and other financing fees	Interest and other financing fees
Equity warrants | Realized gain (loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 0	$ 0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net realized gains (losses) on investments	Net realized gains (losses) on investments
Equity warrants | Unrealized appreciation (depreciation)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ (1,664,000)	$ 208,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net unrealized appreciation (depreciation) on investments	Net unrealized appreciation (depreciation) on investments
Royalty rights
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value beginning of period	$ 5,833,000	$ 0
New investments	0	3,871,000
Investment restructuring	0	0
Transfers into Level 3	0
Transfers out of Level 3	0
Transfers into (out of) Level 3, net		0
Proceeds from sales of investments / return of capital	(4,776,000)	(81,000)
Loan origination fees received	0	0
Principal repayments received	0	0
Fair value end of period	1,581,000	3,819,000
Royalty rights | Payment-in-kind interest / dividends
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 0	0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Total payment-in-kind interest income
Royalty rights | Accretion of loan premium / discount
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 0	0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and other financing fees
Royalty rights | Accretion of deferred loan origination revenue
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 0	0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Interest and other financing fees
Royalty rights | Realized gain (loss)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ 2,467,000	0
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net realized gains (losses) on investments
Royalty rights | Unrealized appreciation (depreciation)
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value recurring basis gain (losses)	$ (1,943,000)	$ 29,000
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net unrealized appreciation (depreciation) on investments

X

- Definition

Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Loan Origination Fees Received

+ References

No definition available.

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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Principal Repayment Received

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No definition available.

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Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Restructuring

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No definition available.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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- Definition

Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

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- Definition

Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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- Definition

Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

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