Amount due from milestone payments net of contractual foreign currency exchange adjustments.

No definition available.

Name:	cara_AmountDueFromMilestonePaymentsNetOfContractualForeignCurrencyExchangeAdjustments
Namespace Prefix:	cara_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount reclassified from collaborative revenue to clinical compound revenue.

+ References

No definition available.

+ Details

Name:	cara_ClinicalCompoundRevenue
Namespace Prefix:	cara_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of cost incurred in the period related to clinical trials included in the research and development deliverable under the Maruishi license agreement.

+ References

No definition available.

+ Details

Name:	cara_ClinicalTrialCostRelatedToResearchAndDevelopmentExpense
Namespace Prefix:	cara_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of revenue recognized in the period from the revenue deferred upon initiation of the Maruishi license agreement. The amount recognized is based on the amount of research and development costs incurred during the period as a percentage of total such costs expected to be incurred to fulfill the research and development deliverable. Also includes a portion of the revenue recognized from nonsubstantive milestones.

+ References

No definition available.

+ Details

Name:	cara_CollaborativeRevenue
Namespace Prefix:	cara_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Contractual foreign currency exchange adjustments.

+ References

No definition available.

+ Details

Name:	cara_ContractualForeignCurrencyExchangeAdjustments
Namespace Prefix:	cara_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Cost of clinical compound sale related to research and development expense.

+ References

No definition available.

+ Details

Name:	cara_CostOfClinicalCompoundSaleRelatedToResearchAndDevelopmentExpense
Namespace Prefix:	cara_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of revenue recognized upon entering into a license agreement with a collaborator combined with cash received upon achievement of a defined milestone by the collaborator.

+ References

No definition available.

+ Details

Name:	cara_LicenseAndMilestoneFeesRevenue
Namespace Prefix:	cara_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Cash payment received upon achievement of a defined milestone by a collaborator.

+ References

No definition available.

+ Details

Name:	cara_MilestonePaymentReceived
Namespace Prefix:	cara_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Milestone payments receivable.

+ References

No definition available.

+ Details

Name:	cara_MilestonePaymentsReceivable
Namespace Prefix:	cara_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount that could be received by the company if the pharmaceutical company achieves the next clinical development milestone defined in the license agreement.

+ References

No definition available.

+ Details

Name:	cara_NextPotentialMilestoneThatCouldBeReceived
Namespace Prefix:	cara_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of items that the company is contractually required to provide to the licensee during the term of the license. Revenue recognized by the company is apportioned among the identified deliverables.

+ References

No definition available.

+ Details

Name:	cara_NumberOfDeliverablesForRevenueRecognized
Namespace Prefix:	cara_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Potential revenue to be recognized if all defined milestones that are to be achieved under the license agreement by the collaborator are actually achieved.

+ References

No definition available.

+ Details

Name:	cara_PotentialRevenueToBeRecognizedFromNonsubstantiveMilestones
Namespace Prefix:	cara_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Potential revenue to be recognized if all defined milestones that are to be achieved by the company under the license agreement are actually achieved.

+ References

No definition available.

+ Details

Name:	cara_PotentialRevenueToBeRecognizedFromSubstantiveMilestones
Namespace Prefix:	cara_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Tax withholding.

+ References

No definition available.

+ Details

Name:	cara_TaxWithholding
Namespace Prefix:	cara_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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

- Definition

The carrying amount of consideration received or receivable as of the balance sheet date on potential earnings that were not recognized as revenue in conformity with GAAP, and which are expected to be recognized as such within one year or the normal operating cycle, if longer, including sales, license fees, and royalties, but excluding interest income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 8

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6935-107765

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 605

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 13.A.4(a).Q1)

-URI http://asc.fasb.org/extlink&oid=27012821&loc=d3e214044-122780

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 13

-Section A

+ Details

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

- Definition

The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 730

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 985

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756

+ Details

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

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=cara_ChongKunDangPharmaceuticalCorporationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=cara_ClinicalDevelopmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=cara_RegulatoryEventsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=cara_MaruishiPharmaceuticalCompanyLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=cara_AmortizationOfDeferredRevenueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Collaborations - Additional Information (Detail) $ in Thousands	1 Months Ended			3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($)	Aug. 31, 2015 USD ($)	Aug. 31, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) Deliverables	Sep. 30, 2014 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2014 USD ($)	Apr. 30, 2012 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Clinical compound revenue						$ 0	$ 159
License and milestone fee revenue				$ 1,710		1,710	302
Collaborative revenue				730	$ 1,125	2,093	1,802
Deferred R&D service revenue									$ 1,452
Research and development expense				5,584	6,208	13,653	11,609
Chong Kun Dang Pharmaceutical Corporation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable										$ 3,750
Milestone payment received	$ 417	$ 209
South Korean Withholding tax	83	$ 41
Next potential milestone that could be received						$ 750
License and milestone fee revenue								$ 1,190
Chong Kun Dang Pharmaceutical Corporation [Member] \| Clinical Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable										2,250
Chong Kun Dang Pharmaceutical Corporation [Member] \| Regulatory Events [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payments receivable										$ 1,500
Maruishi Pharmaceutical Co., Ltd. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Milestone payment received			$ 480
Number of deliverables for revenue recognized \| Deliverables						2
Revenue recognized from nonsubstantive milestones						$ 8,000
Revenue recognized from substantive milestones						2,500
Amount due from milestone payments net of contractual foreign currency exchange adjustments	1,725
Contractual foreign currency exchange adjustments	275
License and milestone fee revenue				1,084		1,084
Collaborative revenue				641		641
Deferred R&D service revenue	$ 0			0		0			$ 1,452
Clinical trial costs related to the R&D services deliverable				108	1,326	1,583	2,324
Research and development expense							2,438
Cost of clinical compound sold to Maruishi							114
Maruishi Pharmaceutical Co., Ltd. [Member] \| Clinical Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Next potential milestone that could be received						1,000
Maruishi Pharmaceutical Co., Ltd. [Member] \| Amortization Of Deferred Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Collaborative revenue				$ 89	$ 1,125	$ 1,452	$ 1,802