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Description Of Business (Percentage Of Consumer Loans Assigned Based On Unit Volumes) (Details) | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Portfolio Program [Member] |  |  |
Description Of Business [Line Items] |  |  |
Percentage of new consumer loans | 90.70%cacc_PercentageOfNewConsumerLoanAssignments / cacc_PaymentsForProceedsFromLoansReceivableProgramsAxis = cacc_PortfolioProgramMember | 93.50%cacc_PercentageOfNewConsumerLoanAssignments / cacc_PaymentsForProceedsFromLoansReceivableProgramsAxis = cacc_PortfolioProgramMember | 93.70%cacc_PercentageOfNewConsumerLoanAssignments / cacc_PaymentsForProceedsFromLoansReceivableProgramsAxis = cacc_PortfolioProgramMember
Purchase Program [Member] |  |  |
Description Of Business [Line Items] |  |  |
Percentage of new consumer loans | 9.30%cacc_PercentageOfNewConsumerLoanAssignments / cacc_PaymentsForProceedsFromLoansReceivableProgramsAxis = cacc_PurchaseProgramMember | 6.50%cacc_PercentageOfNewConsumerLoanAssignments / cacc_PaymentsForProceedsFromLoansReceivableProgramsAxis = cacc_PurchaseProgramMember | 6.30%cacc_PercentageOfNewConsumerLoanAssignments / cacc_PaymentsForProceedsFromLoansReceivableProgramsAxis = cacc_PurchaseProgramMember

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- Definition Percentage Of New Consumer Loan Assignments + References No definition available. + Details
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Namespace Prefix: | cacc_
Data Type: | num:percentItemType
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Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
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