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Description Of Business (Percentage Of Consumer Loans Assigned Based On Unit Volumes) (Details)
 12 Months Ended
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