Loans Receivable (Narrative) (Details)	Mar. 31, 2013
Loans Receivable [Abstract]
Age of Consumer Loans contractual payments due with no forecasted future net cash flows	120 months

Period After Consumer Loans With No Forecasted Future Net Cash Flows

No definition available.

Name:	cacc_PeriodAfterConsumerLoansWithNoForecastedFutureNetCashFlows
Namespace Prefix:	cacc_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant