Quarterly report pursuant to Section 13 or 15(d)

Fair Value of Financial Instruments - Schedule of Fair Value Hierarchy Of Outstanding Borrowings (Details)

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Fair Value of Financial Instruments - Schedule of Fair Value Hierarchy Of Outstanding Borrowings (Details) - USD ($)
$ in Thousands
Mar. 31, 2024
Dec. 31, 2023
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value $ 1,751,998 $ 1,554,869
Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value 1,751,998 1,554,869
Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 1,652,970 1,450,995
SBA Debentures | Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value 170,469 170,323
SBA Debentures | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 147,970 142,011
July 2024 Notes | Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value 104,902 104,828
July 2024 Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 105,145 105,755
February 2025 Notes | Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value 49,895 49,866
February 2025 Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 48,922 49,144
June 2025 Notes | Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value 69,798 69,757
June 2025 Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 68,342 67,198
June 2025 3-Year Notes | Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value 49,810 49,771
June 2025 3-Year Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 49,813 48,983
March 2026 A Notes | Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value 49,818 49,795
March 2026 A Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 47,335 47,702
March 2026 B Notes | Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value 49,802 49,776
March 2026 B Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 47,381 47,759
September 2026 Notes | Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value 322,585 322,339
September 2026 Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 288,832 288,711
January 2027 Notes | Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value 346,266 345,935
January 2027 Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 314,530 315,832
2031 Asset-Backed Notes | Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value 148,691 148,544
2031 Asset-Backed Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 143,700 142,500
2033 Notes | Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value 38,962 38,935
2033 Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 40,000 40,400
MUFG Bank Facility | Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value 136,000 61,000
MUFG Bank Facility | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 136,000 61,000
SMBC Facility | Carrying Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Carrying value 215,000 94,000
SMBC Facility | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 215,000 94,000
Observable Inputs (Level 2) | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 183,700 182,900
Observable Inputs (Level 2) | 2031 Asset-Backed Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 143,700 142,500
Observable Inputs (Level 2) | 2033 Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 40,000 40,400
Unobservable Inputs (Level 3) | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 1,469,270 1,268,095
Unobservable Inputs (Level 3) | SBA Debentures | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 147,970 142,011
Unobservable Inputs (Level 3) | July 2024 Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 105,145 105,755
Unobservable Inputs (Level 3) | February 2025 Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 48,922 49,144
Unobservable Inputs (Level 3) | June 2025 Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 68,342 67,198
Unobservable Inputs (Level 3) | June 2025 3-Year Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 49,813 48,983
Unobservable Inputs (Level 3) | March 2026 A Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 47,335 47,702
Unobservable Inputs (Level 3) | March 2026 B Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 47,381 47,759
Unobservable Inputs (Level 3) | September 2026 Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 288,832 288,711
Unobservable Inputs (Level 3) | January 2027 Notes | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 314,530 315,832
Unobservable Inputs (Level 3) | MUFG Bank Facility | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value 136,000 61,000
Unobservable Inputs (Level 3) | SMBC Facility | Fair Value    
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]    
Approximate Fair Value $ 215,000 $ 94,000