Investments at Fair Value - Schedule of Investments at Fair Value (Details) - USD ($)	9 Months Ended		12 Months Ended
	Sep. 30, 2025		Dec. 31, 2024		Sep. 30, 2024
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	$ 332,569,000	[1],[2],[3]	$ 103,310,000	[4],[5]	$ 103,310,000
Fair Value	333,530,000	[3],[6]	103,947,000	[5],[7],[8]
Net Unrealized Gain (Loss)	961,000		637,000
First-lien debt investments
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	290,889,000		103,310,000
Fair Value	291,693,000		103,947,000
Net Unrealized Gain (Loss)	804,000		$ 637,000
Second-lien debt investments
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	31,217,000
Fair Value	31,369,000
Net Unrealized Gain (Loss)	152,000
Equity and other investments
Debt Securities, Available-for-Sale [Line Items]
Amortized cost	10,463,000
Fair Value	10,468,000
Net Unrealized Gain (Loss)	$ 5,000

[1] As of September 30, 2025, the estimated cost basis of investments for U.S. federal tax purposes was $4,428 resulting in estimated gross unrealized gains and losses of $8,983 and $4,555, respectively.

[2] The amortized cost represents the original cost adjusted for the amortization of discounts and premiums, as applicable, on debt investments using the effective interest method.

[3] Unless otherwise indicated, the Company’s portfolio companies are domiciled in the United States. Under the 1940 Act, the Company would “control” a portfolio company if the Company owned more than 25% of its outstanding voting securities and/or had the power to exercise control over the management or policies of such portfolio company. As of September 30, 2025, the Company does not “control” any of the portfolio companies. Also under the 1940 Act, the Company would be deemed to be an “Affiliated Person” of a portfolio company if the Company owns more than 5% of the portfolio company’s outstanding voting securities. As of September 30, 2025, the Company does not identify any of its portfolio companies as affiliates.

[4] The amortized cost represents the original cost adjusted for the amortization of discounts and premiums, as applicable, on debt investments using the effective interest method.

[5] Unless otherwise indicated, the Company’s portfolio companies are domiciled in the United States. Under the 1940 Act, the Company would “control” a portfolio company if the Company owned more than 25% of its outstanding voting securities and/or had the power to exercise control over the management or policies of such portfolio company. As of December 31, 2024, the Company did not “control” any of the portfolio companies. Also under the 1940 Act, the Company would be deemed to be an “Affiliated Person” of a portfolio company if the Company owns more than 5% of the portfolio company’s outstanding voting securities. As of December 31, 2024, the Company did not identify any of its portfolio companies as affiliates. The amortized cost represents the original cost adjusted for the amortization of discounts and premiums, as applicable, on debt investments using the effective interest method.

[6] In accordance with Financial Accounting Standards Board Accounting Standards Codification Topic 820, Fair Value Measurements (“ASC Topic 820”), unless otherwise indicated, the fair values of all investments were determined using significant unobservable inputs and are considered Level 3 investments. See Note 5 for further information related to investments at fair value.

[7] In accordance with ASC Topic 820, unless otherwise indicated, the fair values of all investments were determined using significant unobservable inputs and are considered Level 3 investments. See Note 5 for further information related to investments at fair value.

[8] As of December 31, 2024, Crestline Lending Solutions, LLC (the “Company”) had not yet elected to be regulated as a business development company (“BDC”), and was operating as Crestline Lending Solutions Ramp, LLC (the “Ramp Vehicle”), a private fund based on an exception from the definition of "investment company" under Section 3(c)(7) of the Investment Company Act of 1940, as amended (the “1940 Act”).