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

Loans and leases receivable transfers.

No definition available.

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

Loans and Leases Receivable, Net [Roll Forward]

No definition available.

Name:	cacc_LoansandLeasesReceivableNetRollForward
Namespace Prefix:	cacc_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

New consumer loan assignments

No definition available.

Name:	cacc_NewConsumerLoanAssignments
Namespace Prefix:	cacc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

Name:	us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(3)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Name:	us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=84173941&loc=d3e5074-111524

Name:	us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

The cash inflow associated with the collection, including prepayments, of loans receivable issued for financing of goods and services.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3179-108585