Revenues - Contract Balances (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022
Contract Balances
Accounts receivable	$ 1,114.6	$ 906.7
Unearned revenues	280.2	291.7
Contracts in transit
Contract Balances
Accounts receivable	361.9	281.7
Vehicle receivables
Contract Balances
Accounts receivable	170.6	235.1
Manufacturer receivables
Contract Balances
Accounts receivable	218.9	178.9
Trade receivables
Contract Balances
Accounts receivable	$ 344.1	$ 191.1

Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable, classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479837/606-10-45-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479806/606-10-50-8

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147479837/606-10-45-2

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant