Stock and Stock-Based Compensation Summary (Details) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
Mar. 31, 2020 USD ($) installment $ / shares shares	Mar. 31, 2019 USD ($)
Stock and Stock-Based Compensation Plans
Stock-based compensation expense (in dollars)	$ 5.0	$ 6.4
PRSUs
Stock and Stock-Based Compensation Plans
Stock-based compensation expense (in dollars)	1.5	3.6
RSUs
Stock and Stock-Based Compensation Plans
Stock-based compensation expense (in dollars)	$ 3.5	$ 2.8
KAR Auction Services, Inc. 2009 Omnibus Stock and Incentive Plan \| RSUs
Stock and Stock-Based Compensation Plans
PRSUs and/or RSUs grants \| shares	0.4
Number of equal annual installments \| installment	3
Weighted average grant date fair value of the PRSUs/RSUs \| $ / shares	$ 22.25
KAR Auction Services, Inc. 2009 Omnibus Stock and Incentive Plan \| PRSUs - Operating Adjusted EPS
Stock and Stock-Based Compensation Plans
PRSUs and/or RSUs grants \| shares	0.4
PRSUs vesting period	3 years
Weighted average grant date fair value of the PRSUs/RSUs \| $ / shares	$ 22.25

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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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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