Name:	knsa_ContractualObligationClinicalAndRegulatoryMilestoneFuturePayments
Namespace Prefix:	knsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of additional specified annual net sales threshold, for the calculation of the milestone payment.

No definition available.

Name:	knsa_ContractualObligationMilestonePaymentAdditionalSalesThreshold
Namespace Prefix:	knsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The amount of annual net sales to be excluded from the calculation of the milestone payment.

No definition available.

Name:	knsa_ContractualObligationMilestonePaymentSalesExcluded
Namespace Prefix:	knsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of future maximum contractual obligation for milestone payment upon the achievement of annual net sales thresholds.

No definition available.

Name:	knsa_ContractualObligationSalesMilestoneFutureMaximumPayments
Namespace Prefix:	knsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of milestone payment to be paid by the company upon the achievement of specified clinical and regulatory milestones.

No definition available.

Name:	knsa_ContractualObligationUponSpecifiedClinicalAndRegulatoryMilestoneAchievement
Namespace Prefix:	knsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The amount of milestone payment commitment remaining to be paid by the company upon the achievement of specified clinical and regulatory milestones.

No definition available.

Name:	knsa_ContractualObligationUponSpecifiedClinicalAndRegulatoryMilestoneAchievementCommitmentRemaining
Namespace Prefix:	knsa_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

The maximum percentage of royalty payable on annual net sales of licensed products on a escalating tiers basis.

No definition available.

Name:	knsa_MaximumPercentageOfRoyaltyPayableOnAnnualNetSalesOfLicensedProducts
Namespace Prefix:	knsa_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The notice period upon which the Company can terminate the agreement in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	knsa_TimePeriodToTerminateAgreement
Namespace Prefix:	knsa_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

The period which both parties can terminate the agreement on uncured material breaches, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	knsa_TimePeriodToTerminateAgreementByBothPartiesUnderUncuredMaterialBreaches
Namespace Prefix:	knsa_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

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.

No definition available.

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

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.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 912
-SubTopic 730
-Section 25
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6472174&loc=d3e58812-109433

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 985
-SubTopic 20
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 730
-SubTopic 10
-Section 50
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373

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

Name:	srt_CounterpartyNameAxis=knsa_MedimmuneLimitedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

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

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: