Loans Receivable Loans Receivable (Summary of Changes in Expected Future Net Cash Flows) (Details) - USD ($) $ in Millions |
3 Months Ended | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Mar. 31, 2026 |
Mar. 31, 2025 |
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| Accounts, Notes, Loans and Financing Receivable [Line Items] | |||||||||||
| Balance, beginning of period | $ 11,610.2 | $ 11,560.2 | |||||||||
| New Consumer Loan Assignments | [1] | 1,556.0 | 1,608.0 | [2] | |||||||
| Realized Net Cash Flows | [3] | (1,423.8) | (1,353.1) | ||||||||
| Forecast changes | (9.1) | (20.9) | |||||||||
| Transfers | [4] | 2.8 | 1.8 | ||||||||
| Balance, end of period | 11,736.1 | 11,796.0 | |||||||||
| Dealer Loans [Member] | |||||||||||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | |||||||||||
| Balance, beginning of period | 8,165.5 | 8,176.3 | |||||||||
| New Consumer Loan Assignments | [1] | 1,084.1 | 1,206.7 | [2] | |||||||
| Realized Net Cash Flows | [3] | (990.5) | (933.7) | ||||||||
| Forecast changes | (9.1) | (24.6) | |||||||||
| Transfers | [4] | (48.5) | (41.5) | ||||||||
| Balance, end of period | 8,201.5 | 8,383.2 | |||||||||
| Purchased Loans [Member] | |||||||||||
| Accounts, Notes, Loans and Financing Receivable [Line Items] | |||||||||||
| Balance, beginning of period | 3,444.7 | 3,383.9 | |||||||||
| New Consumer Loan Assignments | [1] | 471.9 | 401.3 | [2] | |||||||
| Realized Net Cash Flows | [3] | (433.3) | (419.4) | ||||||||
| Forecast changes | 0.0 | 3.7 | |||||||||
| Transfers | [4] | 51.3 | 43.3 | ||||||||
| Balance, end of period | $ 3,534.6 | $ 3,412.8 | |||||||||
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