XML 48 R36.htm IDEA: XBRL DOCUMENT
v3.3.0.814

Description of Business (Percentage of Consumer Loans Assigned Based on Unit Volumes) (Details) | 3 Months Ended
--- | ---
Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014
Portfolio Program [Member] |  |  |  |  |  |  |
Description Of Business [Line Items] |  |  |  |  |  |  |
Percentage of new consumer loans | 87.30% | 87.70% | 88.60% | 89.00% | 90.50% | 91.40% | 91.70%
Purchase Program [Member] |  |  |  |  |  |  |
Description Of Business [Line Items] |  |  |  |  |  |  |
Percentage of new consumer loans | 12.70% | 12.30% | 11.40% | 11.00% | 9.50% | 8.60% | 8.30%

X
- Definition Description Of Business [Line Items] + References No definition available. + Details
Name: | cacc_DescriptionOfBusinessLineItems
Namespace Prefix: | cacc_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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

X
- Details
Name: | cacc_PaymentsForProceedsFromLoansReceivableProgramsAxis=cacc_PortfolioProgramMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | cacc_PaymentsForProceedsFromLoansReceivableProgramsAxis=cacc_PurchaseProgramMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |