Senior Securities - Summary of Senior Securities (Details) - USD ($)	Jun. 30, 2025	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Line Of Credit Facility [Line Items]
Asset Coverage Per Unit	$ 5,604	$ 6,932	$ 5,244	$ 6,906	$ 11,020	$ 9,508	$ 5,812	$ 5,221	$ 6,513	$ 4,056
Asset Coverage Per Unit, Notes	1,698	1,789	1,643	1,929	1,948	2,058	1,992	2,157	2,335	2,352
Operating Facility
Line Of Credit Facility [Line Items]
Total Amount Outstanding	18,000	120,671	163,169	123,890	154,480	120,454	108,498	82,000	57,000	100,500
Involuntary Liquidating Preference Per Unit	0	0	0	0	0	0	0	0	0	0
Funding Facility I
Line Of Credit Facility [Line Items]
Total Amount Outstanding							158,000	212,000	175,000	175,000
Involuntary Liquidating Preference Per Unit	0	0	0	0	0	0	0	0	0	0
Funding Facility II
Line Of Credit Facility [Line Items]
Total Amount Outstanding	100,000	75,000	100,000	100,000	0	36,000
Involuntary Liquidating Preference Per Unit	0	0	0	0	0	0
Merger Sub Facility
Line Of Credit Facility [Line Items]
Total Amount Outstanding	202,000	60,000
Asset Coverage Per Unit	5,604	6,932
Involuntary Liquidating Preference Per Unit	0	0
SBA Debentures
Line Of Credit Facility [Line Items]
Total Amount Outstanding	122,000	131,500	150,000	150,000	150,000	138,000	138,000	98,000	83,000	61,000
Involuntary Liquidating Preference Per Unit	0	0	0	0	0	0	0	0	0	0
2019 Convertible Notes
Line Of Credit Facility [Line Items]
Total Amount Outstanding								108,000	108,000	108,000
Involuntary Liquidating Preference Per Unit	0	0	0	0	0	0	0	0	0	0
2022 Convertible Notes
Line Of Credit Facility [Line Items]
Total Amount Outstanding					140,000	140,000	140,000	140,000	140,000	140,000
Involuntary Liquidating Preference Per Unit	0	0	0	0	0	0	0	0	0	$ 0
2022 Notes
Line Of Credit Facility [Line Items]
Total Amount Outstanding						175,000	175,000	175,000	175,000
Involuntary Liquidating Preference Per Unit	0	0	0	0	0	0	0	$ 0	$ 0
2024 Notes
Line Of Credit Facility [Line Items]
Total Amount Outstanding			250,000	250,000	250,000	250,000	200,000
Involuntary Liquidating Preference Per Unit	0	0	0	0	0	$ 0	$ 0
2025 Notes
Line Of Credit Facility [Line Items]
Total Amount Outstanding	92,000	92,000
Involuntary Liquidating Preference Per Unit	0	0
2026 Notes
Line Of Credit Facility [Line Items]
Total Amount Outstanding	325,000	325,000	325,000	325,000	325,000
Involuntary Liquidating Preference Per Unit	0	0	$ 0	$ 0	$ 0
2029 Notes
Line Of Credit Facility [Line Items]
Total Amount Outstanding	325,000	325,000
Involuntary Liquidating Preference Per Unit	$ 0	$ 0