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Debt (Summary of Debt) (Details) - USD ($) $ in Millions | Mar. 31, 2026 | Dec. 31, 2025 | Mar. 31, 2025 | Feb. 28, 2025 | Dec. 31, 2024 | Dec. 19, 2023 | Mar. 07, 2019
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Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Revolving secured line of credit balance outstanding |  | $ 219.6 | $ 107.3 |  |  |  |  |
Secured Debt |  | 5,100.3 | 5,158.8 |  |  |  |  |
Senior notes balance outstanding |  | 1,088.7 | 1,087.8 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | 525.7 | 477.9 | $ 591.8 |  | $ 501.3 |  |
Revolving Secured Line of Credit [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Revolving secured line of credit balance outstanding |  | 219.6 | 107.3 |  |  |  |  |
Amount available for borrowing | [1] | $ 190.4 | $ 302.7 |  |  |  |  |
Line of credit facility, interest rate |  | 5.64% | 5.69% |  |  |  |  |
Warehouse Facility II [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 251.0 | $ 0.0 |  |  |  |  |
Amount available for borrowing | [1] | 249.0 | 500.0 |  |  |  |  |
Loans pledged as collateral |  | 352.3 | 0.0 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 5.9 | $ 0.0 |  |  |  |  |
Interest rate |  | 5.48% | 0.00% |  |  |  |  |
Warehouse Facility IV [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 0.0 | $ 0.0 |  |  |  |  |
Amount available for borrowing | [1] | 300.0 | 300.0 |  |  |  |  |
Loans pledged as collateral |  | 0.0 | 0.0 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 0.0 | $ 0.0 |  |  |  |  |
Interest rate |  | 0.00% | 0.00% |  |  |  |  |
Warehouse Facility V [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 0.0 | $ 0.0 |  |  |  |  |
Amount available for borrowing | [1] | 250.0 | 250.0 |  |  |  |  |
Loans pledged as collateral |  | 0.0 | 0.0 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 0.0 | $ 1.0 |  |  |  |  |
Interest rate |  | 0.00% | 0.00% |  |  |  |  |
Warehouse Facility VI [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 0.0 | $ 0.0 |  |  |  |  |
Amount available for borrowing | [1] | 75.0 | 75.0 |  |  |  |  |
Loans pledged as collateral |  | 0.0 | 0.0 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 0.0 | $ 0.1 |  |  |  |  |
Interest rate |  | 0.00% | 0.00% |  |  |  |  |
Warehouse Facility VIII [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 0.0 | $ 0.0 |  |  |  |  |
Amount available for borrowing | [1] | 200.0 | 200.0 |  |  |  |  |
Loans pledged as collateral |  | 0.0 | 0.0 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 0.0 | $ 0.0 |  |  |  |  |
Interest rate |  | 0.00% | 0.00% |  |  |  |  |
Term ABS 2019-2 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 500.0 | $ 500.0 |  |  |  |  |
Loans pledged as collateral |  | 522.5 | 523.8 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 47.8 | $ 42.1 |  |  |  |  |
Interest rate |  | 5.43% | 5.43% |  |  |  |  |
Term ABS 2021-1 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 100.0 | $ 100.0 |  |  |  |  |
Loans pledged as collateral |  | 110.6 | 108.8 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 10.0 | $ 8.8 |  |  |  |  |
Interest rate |  | 5.07% | 5.95% |  |  |  |  |
Term ABS 2022-1 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 0.0 | $ 44.8 |  |  |  |  |
Loans pledged as collateral |  | 0.0 | 186.3 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 0.0 | $ 19.7 |  |  |  |  |
Interest rate |  | 0.00% | 6.13% |  |  |  |  |
Term ABS 2022-2 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 300.0 | $ 300.0 |  |  |  |  |
Loans pledged as collateral |  | 320.9 | 325.0 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 27.4 | $ 23.6 |  |  |  |  |
Interest rate |  | 6.09% | 6.12% |  |  |  |  |
Term ABS 2022-3 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 82.0 | $ 127.0 |  |  |  |  |
Loans pledged as collateral |  | 205.3 | 238.8 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 24.8 | $ 23.0 |  |  |  |  |
Interest rate |  | 9.00% | 8.84% |  |  |  |  |
Term ABS 2023-1 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 155.0 | $ 209.2 |  |  |  |  |
Loans pledged as collateral |  | 255.7 | 293.5 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 29.1 | $ 26.9 |  |  |  |  |
Interest rate |  | 7.48% | 7.32% |  |  |  |  |
Term ABS 2023-2 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 183.5 | $ 242.7 |  |  |  |  |
Loans pledged as collateral |  | 295.5 | 338.4 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 31.8 | $ 28.6 |  |  |  |  |
Interest rate |  | 6.91% | 6.69% |  |  |  |  |
Term ABS 2023-3 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 252.4 | $ 312.9 |  |  |  |  |
Loans pledged as collateral |  | 326.9 | 371.3 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 33.0 | $ 30.0 |  |  |  |  |
Interest rate |  | 7.13% | 6.99% |  |  |  |  |
Term ABS 2023-5 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 244.5 | $ 294.0 |  |  |  |  |
Loans pledged as collateral |  | 292.9 | 327.7 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 31.1 | $ 28.9 |  |  |  |  |
Interest rate |  | 6.62% | 6.54% |  |  |  |  |
Term ABS 2024-A [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 200.0 | $ 200.0 |  |  |  |  |
Loans pledged as collateral |  | 210.4 | 211.1 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 18.9 | $ 16.6 |  |  |  |  |
Interest rate |  | 7.45% | 7.45% |  |  |  |  |
Term ABS 2024-1 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 500.0 | $ 500.0 |  |  |  |  |
Loans pledged as collateral |  | 561.5 | 580.2 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 50.6 | $ 44.0 |  |  |  |  |
Interest rate |  | 6.01% | 6.01% |  |  |  |  |
Term ABS 2024-2 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 550.0 | $ 550.0 |  |  |  |  |
Loans pledged as collateral |  | 608.8 | 608.6 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 50.0 | $ 42.9 |  |  |  |  |
Interest rate |  | 6.21% | 6.21% |  |  |  |  |
Term ABS 2024-3 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 600.0 | $ 600.0 |  |  |  |  |
Loans pledged as collateral |  | 658.6 | 668.7 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 55.7 | $ 47.4 |  |  |  |  |
Interest rate |  | 4.91% | 4.91% |  |  |  |  |
Term ABS 2024-B [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 300.0 | $ 300.0 |  |  |  |  |
Loans pledged as collateral |  | 335.9 | 339.9 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 26.7 | $ 22.5 |  |  |  |  |
Interest rate |  | 6.13% | 6.13% |  |  |  |  |
Term ABS 2025-1 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 400.0 | $ 400.0 |  |  |  |  |
Loans pledged as collateral |  | 456.3 | 463.5 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 37.6 | $ 32.1 |  |  |  |  |
Interest rate |  | 5.26% | 5.26% |  |  |  |  |
2026 Senior Notes [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rate |  |  |  |  |  |  |  | 6.625%
2028 Senior Notes [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Senior notes balance outstanding |  | $ 600.0 | $ 600.0 |  |  |  |  |
Interest rate |  | 9.25% | 9.25% |  |  |  | 9.25% |
2030 Senior Notes [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Senior notes balance outstanding |  | $ 500.0 | $ 500.0 |  |  |  |  |
Interest rate |  | 6.625% | 6.625% |  | 6.625% |  |  |
Term ABS 2025-2 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Secured Debt |  | $ 500.0 | $ 500.0 |  |  |  |  |
Loans pledged as collateral |  | 594.4 | 689.8 |  |  |  |  |
Restricted cash and cash equivalents pledged as collateral |  | $ 43.6 | $ 39.0 |  |  |  |  |
Interest rate |  | 4.77% | 4.77% |  |  |  |  |
[1] | Availability may be limited by the amount of assets pledged as collateral.

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