Interim Financial Statements - Fair Value, Assets Held For Sale, Discontinued Operations (Details) $ in Millions	3 Months Ended	12 Months Ended
Mar. 31, 2021 USD ($) item	Dec. 31, 2020 USD ($) item
Fair Value of Financial Instruments
Debt instrument, Carrying Value	$ 1,580.5	$ 1,689.6
Assets Held for Sale and Discontinued Operations
Number of entities newly classified as held for sale \| item	0	0
3.50% senior subordinated notes due 2025
Fair Value of Financial Instruments
Interest rate (as a percent)	3.50%	3.50%
Debt instrument, Carrying Value	$ 543.6	$ 543.2
3.50% senior subordinated notes due 2025 \| Fair Value, Inputs, Level 2
Fair Value of Financial Instruments
Debt instrument, Fair Value	$ 558.1	$ 554.6
5.50% senior subordinated notes due 2026
Fair Value of Financial Instruments
Interest rate (as a percent)	5.50%	5.50%
Debt instrument, Carrying Value	$ 496.6	$ 496.4
5.50% senior subordinated notes due 2026 \| Fair Value, Inputs, Level 2
Fair Value of Financial Instruments
Debt instrument, Fair Value	512.3	515.0
Mortgage facilities
Fair Value of Financial Instruments
Debt instrument, Carrying Value	453.7	458.1
Mortgage facilities \| Fair Value, Inputs, Level 2
Fair Value of Financial Instruments
Debt instrument, Fair Value	$ 456.7	$ 474.7
Retail Automotive Franchise
Disposals
Number of franchises disposed \| item	1

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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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