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Debt (Narrative) (Details) - USD ($) $ in Millions |  |  |  | 3 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2023 | Dec. 19, 2023 | Mar. 07, 2019 | Mar. 31, 2026 | Sep. 30, 2025 | Mar. 31, 2025 | Jun. 30, 2024 | Dec. 31, 2025 | Feb. 28, 2025 | Dec. 18, 2019
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Maximum hedging reserve |  |  |  |  | $ 1.0 |  |  |  |  |  |
Monthly servicing fee as a percentage of collections on newer contributed loans |  |  |  |  | 4.00% |  |  |  |  |  |
Monthly servicing fee for Term ABS financings |  |  |  |  | 4.00% |  |  |  |  |  |
Repayment of senior notes |  |  |  |  | $ 0.0 |  | $ 400.0 |  |  |  |
Loss on extinguishment of debt |  |  |  |  | 0.0 | $ 1.2 | $ 1.2 | $ 1.8 |  |  |
Revolving Secured Line of Credit [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Line of credit facility |  |  |  |  | $ 390.0 |  |  |  |  |  |
Percentage of net book value of loans |  |  |  |  | 80.00% |  |  |  |  |  |
Warehouse Facilities [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Percentage of net book value of loans |  |  |  |  | 80.00% |  |  |  |  |  |
Number of warehouse facilities |  |  |  |  | 5 |  |  |  |  |  |
Senior notes financing amount |  |  |  |  | $ 1,325.0 |  |  |  |  |  |
Warehouse Facility II [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior notes financing amount | [1] |  |  |  | $ 500.0 |  |  |  |  |  |
Senior notes yield to maturity |  |  |  |  | 5.48% |  |  |  | 0.00% |  |
Warehouse Facility IV [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior notes financing amount | [1] |  |  |  | $ 300.0 |  |  |  |  |  |
Senior notes yield to maturity |  |  |  |  | 0.00% |  |  |  | 0.00% |  |
Warehouse Facility V [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior notes financing amount | [1] |  |  |  | $ 250.0 |  |  |  |  |  |
Senior notes yield to maturity |  |  |  |  | 0.00% |  |  |  | 0.00% |  |
Warehouse Facility VI [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior notes financing amount | [1] |  |  |  | $ 75.0 |  |  |  |  |  |
Senior notes yield to maturity |  |  |  |  | 0.00% |  |  |  | 0.00% |  |
Term ABS 2019-2 [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior notes financing amount | [1] |  |  |  | $ 500.0 |  |  |  |  |  |
Senior notes yield to maturity |  |  |  |  | 5.43% |  |  |  | 5.43% |  |
2024 Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior notes financing amount |  |  |  |  |  |  |  |  |  |  | $ 400.0
Repayment of senior notes |  | $ 77.7 | $ 322.3 |  |  |  |  |  |  |  |
Senior notes yield to maturity |  |  |  |  |  |  |  |  |  |  | 5.125%
2026 Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Repayment of senior notes |  |  |  | $ 400.0 |  |  |  |  |  |  |
Senior notes yield to maturity |  |  |  | 6.625% |  |  |  |  |  |  |
2028 Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior notes financing amount |  |  | $ 600.0 |  | $ 600.0 |  |  |  |  |  |
Senior notes yield to maturity |  |  | 9.25% |  | 9.25% |  |  |  | 9.25% |  |
2030 Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Senior notes financing amount |  |  |  |  | $ 500.0 |  |  |  |  | $ 500.0 |
Senior notes yield to maturity |  |  |  |  | 6.625% |  |  |  | 6.625% | 6.625% |
[1] | Financing made available only to a specified subsidiary of the Company.

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