Debt (Schedule Of Debt) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Gross Debt, Current Outstanding	$ 135,869	$ 98,753
Gross Debt, Long-term Outstanding	1,578,666	1,388,495
Debt issuance costs, Current Outstanding	(3,820)	(3,226)
Debt issuance costs, Long-term Outstanding	(7,893)	(7,996)
Total Debt, Current Outstanding	132,049	95,527
Total Debt, Long-term Outstanding	1,570,773	1,380,499
Variable Interest Entity, Primary Beneficiary [Member]
Debt Instrument [Line Items]
Total Debt, Current Outstanding	22,549	30,980
Total Debt, Long-term Outstanding	72,727	74,887
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Gross Debt, Long-term Outstanding	$ 528,000	$ 526,000
Average Interest	3.20%	2.50%
Maturity	Mar. 15, 2020
Revolving Credit Facility [Member] \| CAI Rail [Member]
Debt Instrument [Line Items]
Gross Debt, Long-term Outstanding	$ 272,000	$ 223,500
Average Interest	3.20%	2.40%
Maturity	Oct. 22, 2020
Revolving Credit Facility [Member] \| CAI International GmbH [Member]
Debt Instrument [Line Items]
Gross Debt, Long-term Outstanding	$ 14,736
Average Interest	2.00%	0.00%
Maturity	Sep. 01, 2020
Term Loan [Member] \| CAI Rail [Member]
Debt Instrument [Line Items]
Gross Debt, Current Outstanding	$ 1,198	$ 1,158
Gross Debt, Long-term Outstanding	$ 16,524	$ 17,723
Average Interest	3.40%	3.40%
Maturity	Dec. 22, 2020
Term Loan [Member] \| Development Bank of Japan [Member]
Debt Instrument [Line Items]
Gross Debt, Current Outstanding	$ 21,900	$ 1,800
Gross Debt, Long-term Outstanding		$ 21,900
Average Interest	3.40%	2.90%
Maturity	Apr. 30, 2018
Term Loan [Member] \| Consortium of Banks, Note Dated October 1, 2014 [Member]
Debt Instrument [Line Items]
Gross Debt, Current Outstanding	$ 9,000	$ 9,000
Gross Debt, Long-term Outstanding	$ 111,750	$ 120,750
Average Interest	3.10%	2.30%
Maturity	Oct. 01, 2019
Term Loan [Member] \| Consortium of Banks, Note Dated April 11, 2012 [Member]
Debt Instrument [Line Items]
Gross Debt, Current Outstanding	$ 7,000	$ 7,000
Gross Debt, Long-term Outstanding	$ 82,500	$ 89,500
Average Interest	3.30%	2.50%
Maturity	Jun. 01, 2021
Term Loan [Member] \| Consortium Of Banks Note Dated August 30 2016 [Member]
Debt Instrument [Line Items]
Gross Debt, Current Outstanding	$ 2,805	$ 2,705
Gross Debt, Long-term Outstanding	$ 43,560	$ 46,365
Average Interest	3.60%	3.60%
Maturity	Aug. 01, 2021
Term Loan [Member] \| Variable Interest Entity, Primary Beneficiary [Member]
Debt Instrument [Line Items]
Gross Debt, Current Outstanding		$ 2,287
Gross Debt, Long-term Outstanding	$ 3,286	$ 3,541
Average Interest	2.70%	2.50%
Maturity	Jun. 01, 2019
Senior Secured Notes [Member]
Debt Instrument [Line Items]
Gross Debt, Current Outstanding	$ 6,110	$ 6,110
Gross Debt, Long-term Outstanding	$ 58,885	$ 64,995
Average Interest	4.90%	4.90%
Maturity	Sep. 13, 2022
Asset Backed Notes [Member]
Debt Instrument [Line Items]
Gross Debt, Current Outstanding	$ 65,307	$ 40,000
Gross Debt, Long-term Outstanding	$ 377,984	$ 202,875
Average Interest	3.50%	3.40%
Maturity	Jun. 01, 2042
Collateralized Financing Obligations [Member]
Debt Instrument [Line Items]
Gross Debt, Current Outstanding	$ 22,549	$ 28,693
Gross Debt, Long-term Outstanding	$ 69,441	$ 71,346
Average Interest	1.20%	1.10%
Maturity	Dec. 01, 2020

Debt Instrument Carrying Amount Current

No definition available.

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

- Definition

Debt Instrument Carrying Amount Noncurrent

+ References

No definition available.

+ Details

Name:	cap_DebtInstrumentCarryingAmountNoncurrent
Namespace Prefix:	cap_
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

+ Details

Name:	us-gaap_DebtInstrumentMaturityDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
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

Amount, after accumulated amortization, of debt issuance costs classified as current. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

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 210.5-02.8)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

+ Details

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

- Definition

Amount, after accumulated amortization, of debt issuance costs classified as noncurrent. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

Reference 2: 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)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

+ Details

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

- Definition

Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

+ Details

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

- Details

Name:	dei_LegalEntityAxis=us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
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:	dei_LegalEntityAxis=cap_CaiInternationalGmbhMember
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:	dei_LegalEntityAxis=cap_DevelopmentBankOfJapanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=cap_ConsortiumOfBanksNoteDatedOctober12014Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=cap_ConsortiumOfBanksNoteDatedApril112012Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_LegalEntityAxis=cap_ConsortiumOfBanksNoteDatedAugust302016Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
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_LongtermDebtTypeAxis=us-gaap_CollateralizedDebtObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: