Summary of Significant Accounting Policies (Details) $ in Millions	12 Months Ended
Dec. 31, 2023 USD ($) segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Business Segments
Number of operating segments \| segment	2
Number of reportable segments \| segment	2
Foreign Currency Translation
Foreign currency transaction gain (loss) on intercompany balances	$ 2.9	$ (2.5)	$ (3.8)
Accounts Payable
Book overdrafts	$ 17.9	20.2
Income Taxes
Recognized income tax positions measured at largest amount greater than specified percentage being realized	50.00%
Operating revenues
Provision for credit losses	$ 50.6	9.8	3.5
Finance-related revenue	$ 393.4	375.9	289.2
Purchased vehicles sold as a percentage of total vehicles sold	1.00%
AFC
Operating revenues
Interest income	$ 248.4	202.8	139.7
Fee income	183.3	171.9	144.4
Other revenue	12.3	11.0	8.6
Provision for credit losses	50.6	9.8	3.5
Finance-related revenue	$ 393.4	$ 375.9	$ 289.2
Floorplan receivables \| Minimum
Receivables
Predetermined time period for financing receivables to become due	30 days
Floorplan receivables \| Maximum
Receivables
Predetermined time period for financing receivables to become due	90 days
AFC Funding Corporation \| Minimum
Restricted Cash
Cash reserve as security for the receivables sold (as a percent)	1.00%
Cash reserve as security for the receivables sold - circumstance two (as a percent)	3.00%
AFCI \| Minimum
Restricted Cash
Cash reserve as security for the receivables sold (as a percent)	1.00%
Cash reserve as security for the receivables sold - circumstance two (as a percent)	3.00%

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Amount of fee income including, but not limited to, managerial assistance, servicing of investment, and origination and commitment fees.

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