Debt Instrument Amount Available For Borrowing

No definition available.

Name:	cacc_DebtInstrumentAmountAvailableForBorrowing
Namespace Prefix:	cacc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

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

- 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

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The effective interest rate at the end of the reporting period.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor reclassifies that asset and report that asset in its statement of financial position separately from other assets not so encumbered.

+ References

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+ Details

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

- Definition

Amount of cash and cash equivalents restricted as to withdrawal or usage. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

+ Details

Name:	us-gaap_SecuredDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Debt (Schedule Of Outstanding Debt Amount) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Jan. 17, 2020	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Principal balance outstanding	$ 95.9		$ 0.0
Principal balance outstanding	790.6		1,187.8
Principal balance outstanding	3,711.6		3,339.7
Restricted cash and cash equivalents pledged as collateral	380.2		330.3	$ 303.6
Revolving Secured Line Of Credit [Member]
Debt Instrument [Line Items]
Principal balance outstanding	95.9		0.0
Amount available for borrowing	$ 244.1		$ 340.0
Interest rate	2.02%		0.00%
Warehouse Facility II [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 75.0		$ 0.0
Loans pledged as collateral	91.8		0.0
Restricted cash and cash equivalents pledged as collateral	3.0		1.0
Amount available for borrowing	$ 325.0		$ 400.0
Interest rate	1.90%		0.00%
Warehouse Facility IV [Member]
Debt Instrument [Line Items]
Principal balance outstanding			$ 0.0
Loans pledged as collateral			0.0
Restricted cash and cash equivalents pledged as collateral	$ 1.0		1.0
Amount available for borrowing	$ 300.0		$ 300.0
Interest rate	0.00%		0.00%
Warehouse Facility V [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 0.0
Loans pledged as collateral	0.0
Restricted cash and cash equivalents pledged as collateral	1.0		$ 1.0
Amount available for borrowing	$ 125.0		$ 100.0
Interest rate	0.00%		0.00%
Warehouse Facility VI [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 0.0		$ 0.0
Loans pledged as collateral	0.0		0.0
Restricted cash and cash equivalents pledged as collateral	0.0		0.0
Amount available for borrowing	$ 75.0		$ 75.0
Interest rate	0.00%		0.00%
Warehouse Facility VII [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 0.0		$ 0.0
Loans pledged as collateral	0.0		0.0
Restricted cash and cash equivalents pledged as collateral	1.0		1.0
Amount available for borrowing	$ 150.0		$ 150.0
Interest rate	0.00%		0.00%
Warehouse Facility VIII [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 0.0		$ 0.0
Loans pledged as collateral	0.0		0.0
Restricted cash and cash equivalents pledged as collateral	0.0		0.0
Amount available for borrowing	$ 200.0		$ 200.0
Interest rate	0.00%		0.00%
Term ABS 2016-1 [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 500.0
Loans pledged as collateral	749.3
Restricted cash and cash equivalents pledged as collateral	$ 48.8
Interest rate	2.18%
Term ABS 2016-2 [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 481.8
Loans pledged as collateral	606.6
Restricted cash and cash equivalents pledged as collateral	$ 41.1
Interest rate	1.65%
Term ABS 2016-3 [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 0.0		$ 51.8
Loans pledged as collateral	0.0		219.5
Restricted cash and cash equivalents pledged as collateral	$ 0.0		$ 23.5
Interest rate	0.00%		3.60%
Term ABS 2017-1 [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 0.0		$ 120.9
Loans pledged as collateral	0.0		292.8
Restricted cash and cash equivalents pledged as collateral	$ 0.0		$ 26.1
Interest rate	0.00%		3.19%
Term ABS 2017-2 [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 0.0		$ 277.2
Loans pledged as collateral	0.0		426.7
Restricted cash and cash equivalents pledged as collateral	$ 0.0		$ 35.1
Interest rate	0.00%		2.83%
Term ABS 2017-3 [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 70.9		$ 303.2
Loans pledged as collateral	215.8		393.0
Restricted cash and cash equivalents pledged as collateral	$ 23.2		$ 29.3
Interest rate	3.41%		2.91%
Term ABS 2018-1 [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 196.4		$ 500.0
Loans pledged as collateral	394.1		609.5
Restricted cash and cash equivalents pledged as collateral	$ 36.2		$ 43.8
Interest rate	3.61%		3.24%
Term ABS 2018-2 [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 254.3		$ 450.0
Loans pledged as collateral	410.0		550.4
Restricted cash and cash equivalents pledged as collateral	$ 34.6		$ 37.6
Interest rate	3.85%		3.68%
Term ABS 2018-3 [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 296.1		$ 398.3
Loans pledged as collateral	408.8		487.7
Restricted cash and cash equivalents pledged as collateral	$ 32.9		$ 32.3
Interest rate	3.78%		3.72%
Term ABS 2019-1 [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 402.5		$ 402.5
Loans pledged as collateral	482.3		490.2
Restricted cash and cash equivalents pledged as collateral	$ 35.4		$ 31.9
Interest rate	3.53%		3.53%
Term ABS 2019-2 [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 500.0		$ 500.0
Loans pledged as collateral	575.4		628.5
Restricted cash and cash equivalents pledged as collateral	$ 41.2		$ 38.6
Interest rate	3.13%		3.13%
Term ABS 2019-3 [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 351.7		$ 351.7
Loans pledged as collateral	420.9		428.6
Restricted cash and cash equivalents pledged as collateral	$ 30.8		$ 27.2
Interest rate	2.56%		2.56%
2021 Senior Notes [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 0.0	$ 151.8	$ 151.8	$ 300.0
Interest rate	0.00%		6.125%	6.125%
2023 Senior Notes [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 0.0		$ 250.0
Interest rate	0.00%		7.375%
2024 Senior Notes [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 400.0		$ 400.0
Interest rate	5.125%		5.125%
2026 Senior Notes [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 400.0		$ 400.0
Interest rate	6.625%		6.625%
Mortgage [Member]
Debt Instrument [Line Items]
Principal balance outstanding	$ 10.5		$ 11.3
Interest rate	1.65%		3.21%
TermAssetBackedSecuredFinancingsTwoThousandTwentyThree
Debt Instrument [Line Items]
Principal balance outstanding	$ 600.0
Loans pledged as collateral	759.1
Restricted cash and cash equivalents pledged as collateral	$ 49.3
Interest rate	1.44%