Debt (Non-Recourse Debt) (Details) $ in Millions	Mar. 31, 2026 USD ($) numberOfAgreement	Dec. 31, 2025 USD ($)	May 21, 2025 USD ($)
Debt Instrument [Line Items]
Number of warehouse facility agreements | numberOfAgreement	3
Auto loans receivable	$ 2,444.7	$ 2,209.9
Variable Interest Entity, Primary Beneficiary | Asset Pledged as Collateral
Debt Instrument [Line Items]
Restricted cash of consolidated VIEs	56.9	25.5
Auto loans receivable	1,200.0	551.1
Nonrecourse
Debt Instrument [Line Items]
Non-recourse debt	2,191.0	1,947.3
Less: unamortized debt discounts and debt issuance costs	(5.4)	(2.7)
Less: current maturities	(77.4)	(63.8)
Non-recourse debt, net of current maturities	2,108.2	1,880.8
Nonrecourse | Warehouse facilities
Debt Instrument [Line Items]
Aggregate capacity	1,400.0
Unused capacity	405.6
Remaining borrowing capacity	0.5
Nonrecourse | Warehouse facilities | Line of Credit
Debt Instrument [Line Items]
Non-recourse debt	$ 994.4	$ 1,398.7
Weighted-average annual interest rate	4.50%	4.70%
Nonrecourse | Warehouse Facility, August 2026 expiration
Debt Instrument [Line Items]
Aggregate capacity	$ 400.0
Nonrecourse | Warehouse facility, October 2026 expiration
Debt Instrument [Line Items]
Aggregate capacity	300.0
Nonrecourse | Warehouse Facility, December 2026 expiration
Debt Instrument [Line Items]
Aggregate capacity	700.0
Nonrecourse | Term securitization debt | Variable Interest Entity, Primary Beneficiary | Notes Payable, Other Payables
Debt Instrument [Line Items]
Non-recourse debt	1,196.6	$ 548.6
Nonrecourse | ANF Auto Receivables Trust 2026-1 | Variable Interest Entity, Primary Beneficiary | Notes Payable, Other Payables
Debt Instrument [Line Items]
Non-recourse debt	$ 703.3
Initial principal amount			$ 749.2
Nonrecourse | ANF Auto Receivables Trust 2026-1 | Variable Interest Entity, Primary Beneficiary | Minimum | Notes Payable, Other Payables
Debt Instrument [Line Items]
Percentage interest	3.93%
Nonrecourse | ANF Auto Receivables Trust 2026-1 | Variable Interest Entity, Primary Beneficiary | Maximum | Notes Payable, Other Payables
Debt Instrument [Line Items]
Percentage interest	5.07%
Nonrecourse | ANF Auto Receivables Trust 2025-1 [Member] | Variable Interest Entity, Primary Beneficiary | Notes Payable, Other Payables
Debt Instrument [Line Items]
Non-recourse debt	$ 493.3
Initial principal amount			$ 700.0
Nonrecourse | ANF Auto Receivables Trust 2025-1 [Member] | Variable Interest Entity, Primary Beneficiary | Minimum | Notes Payable, Other Payables
Debt Instrument [Line Items]
Percentage interest	4.62%
Nonrecourse | ANF Auto Receivables Trust 2025-1 [Member] | Variable Interest Entity, Primary Beneficiary | Maximum | Notes Payable, Other Payables
Debt Instrument [Line Items]
Percentage interest	5.63%