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Debt (Schedule of Outstanding Term ABS Financings) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
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Mar. 31, 2015
Term ABS 2012-2 [Member] |  |
Debt Instrument [Line Items] |  |
Close Date | Sep. 20, 2012 |
Net Book Value of Loans Contributed at Closing | $ 315.1 cacc_NetBookValueOfLoansPledgedAsCollateral / us-gaap_DebtInstrumentAxis = cacc_TermAssetBackedSecuredFinancingsTwoThousandTwelveTwoMember |
Maturity Date | Sep. 15, 2014 | [1],[2]
Term ABS 2013-1 [Member] |  |
Debt Instrument [Line Items] |  |
Close Date | Apr. 25, 2013 |
Net Book Value of Loans Contributed at Closing | 187.8 cacc_NetBookValueOfLoansPledgedAsCollateral / us-gaap_DebtInstrumentAxis = cacc_TermAssetBackedSecuredFinancingsTwoThousandThirteenOneMember |
Maturity Date | Apr. 15, 2015 | [1],[2]
Term ABS 2013-2 [Member] |  |
Debt Instrument [Line Items] |  |
Close Date | Oct. 31, 2013 |
Net Book Value of Loans Contributed at Closing | 250.1 cacc_NetBookValueOfLoansPledgedAsCollateral / us-gaap_DebtInstrumentAxis = cacc_TermAssetBackedSecuredfinancingsTwoThousandThirteenTwoMember |
Maturity Date | Oct. 15, 2015 | [1],[2]
Term ABS 2014-1 [Member] |  |
Debt Instrument [Line Items] |  |
Close Date | Apr. 16, 2014 |
Net Book Value of Loans Contributed at Closing | 374.7 cacc_NetBookValueOfLoansPledgedAsCollateral / us-gaap_DebtInstrumentAxis = cacc_TermAssetBackedSecuredFinancingsTwoThousandFourteenOneMember |
Maturity Date | Apr. 15, 2016 | [1],[2]
Term ABS 2014-2 [Member] |  |
Debt Instrument [Line Items] |  |
Close Date | Sep. 25, 2014 |
Net Book Value of Loans Contributed at Closing | 437.6 cacc_NetBookValueOfLoansPledgedAsCollateral / us-gaap_DebtInstrumentAxis = cacc_TermAssetBackedSecuredFinancingsTwoThousandFourteenTwoMember |
Maturity Date | Sep. 15, 2016 | [1],[2]
Term ABS 2015-1 [Member] |  |
Debt Instrument [Line Items] |  |
Close Date | Jan. 29, 2015 |
Net Book Value of Loans Contributed at Closing | $ 375.9 cacc_NetBookValueOfLoansPledgedAsCollateral / us-gaap_DebtInstrumentAxis = cacc_TermAssetBackedSecuredFinancingsTwoThousandFifteenOneMember |
Maturity Date | Jan. 16, 2017 | [1],[2]
[1] | Represents the revolving maturity date. The outstanding balance will amortize after the maturity date based on the cash flows of the pledged assets.
[2] | Financing made available only to a specified subsidiary of the Company.

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- Definition Debt financing close date + References No definition available. + Details
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- Definition Net Book Value Of Loans Pledged As Collateral + References No definition available. + Details
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- Definition Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(2)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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