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Loans Receivable (Summary of Provision for Credit Losses) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | $ 736.2 | $ 481.4 | $ 8.4
Dealer Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | 427.7 | 240.4 | (28.2)
Purchased Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | 308.5 | 241.0 | 36.6
New Consumer Loan assignments |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | 322.5 | 343.7 | 365.1
New Consumer Loan assignments | Dealer Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | 146.2 | 154.8 | 153.1
New Consumer Loan assignments | Purchased Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | 176.3 | 188.9 | 212.0
Forecast Changes [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | 413.7 | 137.7 | (356.7)
Forecast Changes [Member] | Dealer Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | 281.5 | 85.6 | (181.3)
Forecast Changes [Member] | Purchased Loans [Member] |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |
Provision for credit losses | $ 132.2 | $ 52.1 | $ (175.4)

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- Definition Amount of expense related to estimated loss from loan and lease transactions. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 45 -Paragraph 28 -Subparagraph (a) -SubTopic 10 -Topic 230 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482740/230-10-45-28 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section 50 -Paragraph 11B -Subparagraph (c)(2) -SubTopic 10 -Topic 310 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481962/310-10-50-11B Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 220 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.11) -Publisher FASB -URI https://asc.fasb.org//1943274/2147483589/942-220-S99-1 + Details
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