Name:	cacc_AcceleratedPaymentsOfDealerHoldback
Namespace Prefix:	cacc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The cash outflow for non-recourse payments made to dealers under a portfolio program in exchange for the right to service the underlying consumer loans.

No definition available.

Name:	cacc_AdvancesToDealers
Namespace Prefix:	cacc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The cash outflow for payments made to dealers under our Portfolio Program from the portion of the collections on the underlying consumer loans that exceed amounts retained by us to recover the advance balance, certain collection costs, and our servicing fee.

No definition available.

Name:	cacc_PaymentsOfDealerHoldback
Namespace Prefix:	cacc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Percentage Of Accelerated Payments Of Dealer Holdback

No definition available.

Name:	cacc_PercentageOfAcceleratedPaymentsOfDealerHoldback
Namespace Prefix:	cacc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage Of Advances To Dealers

No definition available.

Name:	cacc_PercentageOfAdvancesToDealers
Namespace Prefix:	cacc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage Of Payments Of Dealer Holdback

No definition available.

Name:	cacc_PercentageOfPaymentsOfDealerHoldback
Namespace Prefix:	cacc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Percentage Of Related Party Transaction Revenues From Transaction

No definition available.

Name:	cacc_PercentageOfRelatedPartyTransactionRevenuesFromTransaction
Namespace Prefix:	cacc_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

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.

No definition available.

Name:	us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07.1(c))
-URI http://asc.fasb.org/extlink&oid=114873854&loc=SL114874292-224272

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(e))
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227