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Multiemployer Pension Plans (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($) agreements store	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Multiemployer Plans [Line Items]
Contributions of AutoNation, insignificant plans	$ 0.1	$ 0.1	$ 0.1
Total Contributions	1.7	1.9	1.7
Automotive Industries Pension Plan [Member]
Multiemployer Plans [Line Items]
Contributions of AutoNation, significant plans	$ 1.4	1.6	1.4
Surcharge imposed	Yes
Surcharges paid	$ 0.6	$ 0.8	0.6
Pension protection act zone status	Red	Red
Number of collective-bargaining arrangements that require contributions to the Plan | agreements	3
Potential withdrawal obligation	$ 15.0
IAM National Pension Plan [Member]
Multiemployer Plans [Line Items]
Contributions of AutoNation, significant plans	$ 0.2	$ 0.2	$ 0.2
Surcharge imposed	Yes
Pension protection act zone status	Red	Red
Potential withdrawal obligation	$ 3.0
Collective Bargaining Agreement, Expiration Date, December 31, 2019 [Member] | Automotive Industries Pension Plan [Member]
Multiemployer Plans [Line Items]
Number of collective-bargaining arrangements that require contributions to the Plan | agreements	1
Collective Bargaining Agreement, Expiration Date, December 31, 2021 [Member] | Automotive Industries Pension Plan [Member]
Multiemployer Plans [Line Items]
Number of collective-bargaining arrangements that require contributions to the Plan | agreements	1
Collective Bargaining Agreement, Expiration Date, December 31, 2022 [Member] | Automotive Industries Pension Plan [Member]
Multiemployer Plans [Line Items]
Number of collective-bargaining arrangements that require contributions to the Plan | agreements	1
Collective Bargaining Agreement, Expiration Date, August 31, 2022 [Member] | IAM National Pension Plan [Member]
Multiemployer Plans [Line Items]
Number of collective-bargaining arrangements that require contributions to the Plan | agreements	2
Dealerships [Member]
Multiemployer Plans [Line Items]
Number of stores | store	230
Dealerships [Member] | Multiemployer Plans, Pension [Member]
Multiemployer Plans [Line Items]
Number of stores | store	5

X

- Definition

Amount of surcharge paid by an employer to the pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

No definition available.

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- Definition

The number of collective-bargaining agreements that require contributions to multiemployer pension plans.

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- Definition

Amount of withdrawal liability that could be assessed in the event an entity ceases participating in a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

No definition available.

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- Definition

Amount of cost for employer contribution to multiemployer plan. Multiemployer plan includes, but is not limited to, pension plan determined to be individually significant and insignificant and other postretirement benefit plan.

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Amount of cost for employer contribution to multiemployer pension plan determined to be individually insignificant.

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- Definition

Indicates certified zone status of multiemployer pension plan determined to be individually significant. Acceptable values are "Green", "Yellow", "Orange", "Red", "Other", and "NA".

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Indicates whether employer paid surcharge to multiemployer pension plan determined to be individually significant. Acceptable values are "No", "Yes" and "NA".

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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