Line of Credit Facility, Additional Amount of Borrowing Capacity without Approval

No definition available.

Name:	cap_LineOfCreditFacilityAdditionalAmountOfBorrowingCapacityWithoutApproval
Namespace Prefix:	cap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The maximum amount of borrowing capacity that the line of credit facility might be increased to with possible considerations or restrictions.

+ References

No definition available.

+ Details

Name:	cap_LineOfCreditFacilityMaximumIncreasedAmountOfBorrowingCapacity
Namespace Prefix:	cap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line of Credit Facility, Maximum Total Leverage Ratio

+ References

No definition available.

+ Details

Name:	cap_LineOfCreditFacilityMaximumTotalLeverageRatio
Namespace Prefix:	cap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of quarterly installments for the debt specified in the agreement.

+ References

No definition available.

+ Details

Name:	cap_NumberOfQuarterlyInstallments
Namespace Prefix:	cap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

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

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of the required periodic payments including both interest and principal payments.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

+ Details

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

- Definition

Amount of the required periodic payments applied to principal.

+ References

+ Details

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

- Definition

Amount of payment greater than the preceding installment payments to be paid at final maturity date of debt.

+ References

No definition available.

+ Details

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

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

The cash inflow from amounts received from issuance of long-term debt that is wholly or partially secured by collateral. Excludes proceeds from tax exempt secured debt.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3255-108585

+ Details

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

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=cap_ConsortiumOfBanksMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=cap_CaiRailIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cap_ThirdAmendedAndRestatedRevolvingCreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cap_ClassAssetBackedNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cap_ClassBAssetBackedNotesMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cap_ClassSeries20182AssetBackedNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cap_ClassBSeries20182AssetBackedNotesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_LoansPayableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=cap_TermLoanOctober182023Member
Namespace Prefix:
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Debt (Narrative) (Details)							9 Months Ended
Debt (Narrative) (Details)	Oct. 22, 2018 USD ($)	Oct. 18, 2018 USD ($) item	Sep. 19, 2018 USD ($)	Jun. 27, 2018 USD ($)	Apr. 19, 2018 USD ($) item	Feb. 28, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Available borrowing capacity							$ 151,900,000
Average interest rate							3.90%	3.20%
Debt instrument maturity date							Jun. 01, 2023
Maximum credit commitment				$ 960,000,000
Maximum total leverage ratio				3.75
Revolving Credit Facility [Member] \| Consortium of Banks [Member]
Debt Instrument [Line Items]
Available borrowing capacity							$ 1,157,200,000
Letters of credit outstanding							$ 100,000
Revolving Credit Facility [Member] \| CAI Rail [Member]
Debt Instrument [Line Items]
Average interest rate							3.70%	3.20%
Debt instrument maturity date							Oct. 01, 2020
Maximum credit commitment							$ 500,000,000
Maximum total leverage ratio							3.75
Revolving Credit Facility [Member] \| Third Amended and Restated Revolving Credit Agreement [Member]
Debt Instrument [Line Items]
Maximum credit commitment increase amount				$ 1,100,000,000
Additional credit facility increase without approval				$ 250,000,000
Maximum total leverage ratio				4.00
Asset Backed Notes [Member] \| Class A Asset-Backed Notes [Member]
Debt Instrument [Line Items]
Proceeds from notes						$ 332,000,000
Average interest rate						4.00%
Asset Backed Notes [Member] \| Class B Asset-Backed Notes [Member]
Debt Instrument [Line Items]
Proceeds from notes						$ 16,900,000
Average interest rate						4.80%
Asset Backed Notes [Member] \| Class A Series 2018-2 Asset-Backed Notes [Member]
Debt Instrument [Line Items]
Proceeds from notes			$ 331,500,000
Average interest rate			4.30%
Asset Backed Notes [Member] \| Class B Series 2018-2 Asset-Backed Notes [Member]
Debt Instrument [Line Items]
Proceeds from notes			$ 12,000,000
Average interest rate			5.20%
Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument maturity date					Apr. 30, 2023
Principal amount of loan					$ 30,000,000
Term of loan					5 years
Number of quarterly installments \| item					19
Proceeds used to repay loan					$ 500,000
Debt Instrument Balloon Payment					$ 21,500,000
Term Loan [Member] \| CAI Rail [Member]
Debt Instrument [Line Items]
Average interest rate							3.40%	3.40%
Debt instrument maturity date							Dec. 01, 2020
Subsequent Event [Member] \| Third Amended and Restated Revolving Credit Agreement [Member] \| CAI Rail [Member]
Debt Instrument [Line Items]
Debt instrument maturity date	Oct. 23, 2023
Maximum credit commitment	$ 550,000,000
Maximum credit commitment increase amount	$ 150,000,000
Maximum total leverage ratio	4.00
Subsequent Event [Member] \| Term Loan [Member] \| Term Loan, October 18, 2023 [Member]
Debt Instrument [Line Items]
Average interest rate		4.60%
Principal amount of loan		$ 100,000,000
Term of loan		5 years
Number of quarterly installments \| item		20
Quarterly payments		$ 1,500,000
Debt Instrument Balloon Payment		$ 70,000,000