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Represents the cash reserve maintained when certain circumstances are triggered as a percentage of finance receivables securitized, which serves as security for the obligations collaterized by the financing receivables.

No definition available.

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Data Type:	dtr-types1:percentItemType
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The carrying amount, as of the date of the latest financial statement presented, of finance receivables which are owned but transferred to serve as collateral for the payment of the related debt obligation, primarily a secured borrowing or repurchase agreement, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

No definition available.

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Balance Type:	debit
Period Type:	instant

Reflects other additions and reductions to the finance receivable allowance, which are not reflected elsewhere or separately disclosed.

No definition available.

Name:	kar_FinancingReceivableAllowanceForCreditLossesOther
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Represents the amount of committed liquidity provided by the funding corporation.

No definition available.

Name:	kar_FinancingReceivableCommittedLiquidity
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Represents the number of days for defining financing receivables as past due.

No definition available.

Name:	kar_FinancingReceivablePastDueNumberOfDays
Namespace Prefix:	kar_
Data Type:	xbrli:durationItemType
Balance Type:	na
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Gross amount of liabilities associated with financial assets accounted for as secured borrowings recognized in the transferor's statement of financial position at the end of each period presented.

No definition available.

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Namespace Prefix:	kar_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Amount of allowance for credit loss on financing receivable, classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount of net credit losses charged off.

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Name:	us-gaap_AssetsThatContinueToBeRecognizedSecuritizedOrAssetBackedFinancingArrangementAssetsAndAnyOtherFinancialAssetsManagedTogetherNetCreditLossesDuringPeriod
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Data Type:	xbrli:monetaryItemType
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Amount of increase in allowance for credit loss on financing receivable from recovery.

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-Topic 326
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

No definition available.

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Amount of writeoff of financing receivable, charged against allowance for credit loss.

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-Topic 326
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Amount of expense related loan transactions, lease transactions, credit loss from transactions other than loan and lease transactions, and other loss based on assessment of uncollectability from the counterparty to reduce the account to their net realizable value.

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Name:	us-gaap_ProvisionForLoanLeaseAndOtherLosses
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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This is the amount of the financial instruments that are considered delinquent (past due) at the end of the period.

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-Name Accounting Standards Codification
-Topic 860
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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.

No definition available.

Name:	us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherLineItems
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Data Type:	xbrli:stringItemType
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Amount of transferred financial assets in which the transferor has continuing involvement with the assets underlying the transaction that continue to be recognized in the statement of financial position. Includes, but is not limited to, servicing, recourse, and restrictions on transferor's interests in transferred financial assets.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Name:	us-gaap_SecuritizedAssetsAndAnyOtherFinancialAssetsManagedTogetherPrincipalAmountOutstanding
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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Carrying amount of liabilities associated with financial assets accounted for as secured borrowings recognized in the transferor's statement of financial position at the end of each period presented.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 30
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-Section 50
-Paragraph 1A
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

No definition available.

Name:	us-gaap_UnamortizedDebtIssuanceExpense
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Name:	us-gaap_FinancialInstrumentAxis=kar_FloorplanReceivablesMember
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Name:	us-gaap_FinancialInstrumentAxis=kar_OtherLoansMember
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Data Type:	na
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Name:	dei_LegalEntityAxis=kar_AFCMember
Namespace Prefix:
Data Type:	na
Balance Type:
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Name:	srt_RangeAxis=srt_MinimumMember
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Name:	dei_LegalEntityAxis=kar_AFCFundingCorporationMember
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