XML 21 R41.htm IDEA: XBRL DOCUMENT
v3.19.3

Summary of Significant Accounting Policies New Accounting Pronouncements (Narrative) (Details) - ASU 2016-13 [Member] | 9 Months Ended
--- | ---
Sep. 30, 2019
Minimum [Member] | Net Income [Member] |
Item Effected [Line Items] |
New Accounting Pronouncement Estimated Impact | 30.00%
Minimum [Member] | Loans Receivable [Member] |
Item Effected [Line Items] |
New Accounting Pronouncement Estimated Impact | 30.00%
Minimum [Member] | Allowance for Credit Losses [Member] |
Item Effected [Line Items] |
New Accounting Pronouncement Estimated Impact | 12.00%
Maximum [Member] | Net Income [Member] |
Item Effected [Line Items] |
New Accounting Pronouncement Estimated Impact | 60.00%
Maximum [Member] | Loans Receivable [Member] |
Item Effected [Line Items] |
New Accounting Pronouncement Estimated Impact | 40.00%
Maximum [Member] | Allowance for Credit Losses [Member] |
Item Effected [Line Items] |
New Accounting Pronouncement Estimated Impact | 15.00%

X
- Definition New Accounting Pronouncement Estimated Impact + References No definition available. + Details
Name: | cacc_NewAccountingPronouncementEstimatedImpact
Namespace Prefix: | cacc_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition 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. + References No definition available. + Details
Name: | us-gaap_ItemEffectedLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | srt_RangeAxis=srt_MinimumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ProspectiveAdoptionOfNewAccountingPronouncementsAxis=us-gaap_NewAccountingPronouncementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_IncomeStatementLocationAxis=cacc_NetIncomeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=us-gaap_LoansReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_BalanceSheetLocationAxis=cacc_AllowanceforCreditLossesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_RangeAxis=srt_MaximumMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |