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- Definition

Period After Determination Dealer Loan Write Off

+ References

No definition available.

+ Details

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Balance Type:	na
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- Definition

Period After Determination Purchased Loan Write Off

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
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- Definition

Revenue From Enrollment And Registration Fees In Program

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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Data Type:	xbrli:stringItemType
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- Definition

Threshold To Determine Probability

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No definition available.

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Data Type:	num:percentItemType
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- Definition

Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 720

-SubTopic 35

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6420018&loc=d3e36677-107848

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Balance Type:	debit
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The amount of cash as of the balance sheet date that is not insured by the Federal Deposit Insurance Corporation.

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No definition available.

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

The amount of the cost recognized during the period for defined contribution plans.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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- Definition

Percentage employer matches of the employee's percentage contribution matched.

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No definition available.

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Balance Type:	na
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- Definition

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

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No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
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- Definition

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Describes the periods of time over which an entity anticipates to receive utility from its property, plant and equipment (that is, the periods of time over which an entity allocates the initial cost of its property, plant and equipment).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367646&loc=d3e18780-107790

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-URI http://asc.fasb.org/subtopic&trid=2155824

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- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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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 210.5-02.17)

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

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Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=cacc_DataProcessingEquipmentMember
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Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=us-gaap_BuildingImprovementsMember
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Summary Of Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 portfolio_segment segment	Dec. 31, 2013	Dec. 31, 2012
Summary Of Significant Accounting Policies [Line Items]
Number of Portfolio Segments	2cacc_NumberofPortfolioSegments
Number of Reportable Segments	1us-gaap_NumberOfReportableSegments
Monthly fee charged Dealer in Portfolio Program	$ 599cacc_MonthlyFeePortfolioProgram
One-time enrollment fee in program	9,850
Percentage of first accelerated Dealer Holdback payment retained	50.00%cacc_PaymentHoldbackPercentage
Percentage of enrollment fee of first accelerated dealer holdback payment	50.00%
Period after Consumer Loan assignment that Dealer Loans written off	120 months
Period after month of purchase that Purchased Loans written off	120 months
Unamortized debt issuance expense	16,100,000us-gaap_UnamortizedDebtIssuanceExpense	15,100,000us-gaap_UnamortizedDebtIssuanceExpense
Threshold to determine likelihood of being sustained	50.00%cacc_ThresholdToDetermineProbability
Maximum matching contribution	3.50%
Recognized compensation expense	2,500,000	2,200,000	1,800,000
Advertising expense	300,000us-gaap_AdvertisingExpense	200,000us-gaap_AdvertisingExpense	200,000us-gaap_AdvertisingExpense
Cash and Cash Equivalents [Member]
Summary Of Significant Accounting Policies [Line Items]
Uninsured cash and cash equivalents	5,800,000	3,600,000
Restricted Cash And Cash Equivalents [Member]
Summary Of Significant Accounting Policies [Line Items]
Uninsured cash and cash equivalents	$ 155,300,000	$ 109,500,000
Initial [Member]
Summary Of Significant Accounting Policies [Line Items]
Employer matching contribution, match percentage	100.00%
Matching contribution	1.00%
Additional [Member]
Summary Of Significant Accounting Policies [Line Items]
Employer matching contribution, match percentage	50.00%
Matching contribution	5.00%
Building [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	P40Y
Building Improvements [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	P10Y
Data Processing Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	P3Y
Software [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	P5Y
Office Furniture And Equipment [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	P7Y
Leasehold Improvements [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	P7Y
Software Development [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful lives	P5Y