Name:	cart_FinancingReceivableModificationsTroubledDebtRestructuredLoansAbstract
Namespace Prefix:	cart_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of receivable balance of impaired financing receivables modified by troubled debt restructurings.

No definition available.

Name:	cart_FinancingReceivablesImpairedTroubledDebtRestructurings
Namespace Prefix:	cart_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Refers to financing receivables modified by troubled debt restructurings as percentage of aggregate loans.

No definition available.

Name:	cart_FinancingReceivablesTroubledDebtRestructuringAsPercentageOfAggregateLoans
Namespace Prefix:	cart_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Recorded investment in financing receivables identified as troubled debt restructurings and still accruing interest.

No definition available.

Name:	cart_FinancingReceivablesTroubledDebtRestructuringsAccruingInterest
Namespace Prefix:	cart_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Refers to number of loans in financing receivables identified as troubled debt restructurings with accruing interest.

No definition available.

Name:	cart_FinancingReceivablesTroubledDebtRestructuringsAccruingInterestNumberOfLoans
Namespace Prefix:	cart_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- References

No definition available.

Name:	cart_TroubledDebtRestructuringsBreakdownByTypesOfConcessionsAbstract
Namespace Prefix:	cart_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Number of financing receivables that have been modified by troubled debt restructurings.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

Name:	us-gaap_FinancingReceivableModificationsNumberOfContracts2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Post-modification amount of investment in financing receivables modified by troubled debt restructurings.

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Pre-modification amount of investment in financing receivables modified by troubled debt restructurings.

Name:	us-gaap_FinancingReceivableModificationsPreModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Unused amount of commitments to extend credit to customers.

No definition available.

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

Name:	us-gaap_LoanRestructuringModificationAxis=us-gaap_PrincipalForgivenessMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: