Interim Financial Statements - Fair Value, Assets Held For Sale, Discontinued Operations (Details) $ in Millions	3 Months Ended
Mar. 31, 2020 USD ($) item	Dec. 31, 2019 USD ($)
Fair Value of Financial Instruments
Debt instrument, Carrying Value	$ 2,620.7	$ 2,360.3
Assets Held for Sale and Discontinued Operations
Number of entities newly classified as held for sale \| item	0
3.75% senior subordinated notes due 2020
Fair Value of Financial Instruments
Interest rate (as a percent)	3.75%	3.75%
Debt instrument, Carrying Value	$ 299.5	$ 299.2
3.75% senior subordinated notes due 2020 \| Fair Value, Inputs, Level 2
Fair Value of Financial Instruments
Debt instrument, Fair Value	$ 291.3	$ 302.6
5.75% senior subordinated notes due 2022
Fair Value of Financial Instruments
Interest rate (as a percent)	5.75%	5.75%
Debt instrument, Carrying Value	$ 547.9	$ 547.6
5.75% senior subordinated notes due 2022 \| Fair Value, Inputs, Level 2
Fair Value of Financial Instruments
Debt instrument, Fair Value	$ 514.4	$ 556.7
5.375% senior subordinated notes due 2024
Fair Value of Financial Instruments
Interest rate (as a percent)	5.375%	5.375%
Debt instrument, Carrying Value	$ 298.2	$ 298.0
5.375% senior subordinated notes due 2024 \| Fair Value, Inputs, Level 2
Fair Value of Financial Instruments
Debt instrument, Fair Value	$ 249.9	$ 306.7
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	$ 495.9	$ 495.7
5.50% senior subordinated notes due 2026 \| Fair Value, Inputs, Level 2
Fair Value of Financial Instruments
Debt instrument, Fair Value	437.1	521.7
Mortgage facilities
Fair Value of Financial Instruments
Debt instrument, Carrying Value	416.7	423.2
Mortgage facilities \| Fair Value, Inputs, Level 2
Fair Value of Financial Instruments
Debt instrument, Fair Value	$ 446.1	$ 430.9
Retail Automotive Franchise
Disposals
Number of franchises disposed \| item	4

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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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