Base rent annual increase over the lease term.

No definition available.

Name:	kymr_BaseRentAnnualIncreaseOverTheLeaseTerm
Namespace Prefix:	kymr_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Lease additional term.

+ References

No definition available.

+ Details

Name:	kymr_LeaseAdditionalTerm
Namespace Prefix:	kymr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Lease commencement date.

+ References

No definition available.

+ Details

Name:	kymr_LeaseCommencementDate
Namespace Prefix:	kymr_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Lease term.

+ References

No definition available.

+ Details

Name:	kymr_LeaseTerm
Namespace Prefix:	kymr_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Rental And Lease Expenses

+ References

No definition available.

+ Details

Name:	kymr_RentalAndLeaseExpenses
Namespace Prefix:	kymr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Tenant incentive allowance receivable.

+ References

No definition available.

+ Details

Name:	kymr_TenantIncentiveAllowanceReceivable
Namespace Prefix:	kymr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Area of a real estate property.

+ References

No definition available.

+ Details

Name:	us-gaap_AreaOfRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

Date which lease or group of leases is set to expire, in YYYY-MM-DD format.

+ References

No definition available.

+ Details

Name:	us-gaap_LeaseExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
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_LesseeLeaseDescriptionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Cash payments to lessor's for use of assets under operating leases.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3536-108585

+ Details

Name:	us-gaap_PaymentsForRent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The amount of an asset, typically cash, provided to a counterparty to provide certain assurance of performance by the entity pursuant to the terms of a written or oral agreement, such as a lease.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(17))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Details

Name:	srt_StatementGeographicalAxis=kymr_WatertownMassachusettsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_BalanceSheetLocationAxis=kymr_RestrictedCashMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_LetterOfCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LeaseContractualTermAxis=kymr_TwoThousandNineteenLeaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LeaseContractualTermAxis=kymr_TwoThousandTwentyOneLeaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

Leases - Additional Information (Details) - Watertown, Massachusetts $ in Millions		1 Months Ended	9 Months Ended	12 Months Ended
	Dec. 20, 2021 USD ($) ft²	Oct. 31, 2019 ft²	Sep. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Lessee Lease Description [Line Items]
Lease term	134 months
Noncancelable Facility Lease Agreement
Lessee Lease Description [Line Items]
Area of office space \| ft²	100,624	34,522
Lease term		120 months
Lease expiration date		Mar. 31, 2030
Lease additional term	5 years	5 years
Tenant incentive allowance receivable	$ 20.1
Base Rent	$ 0.8
Annual increase percentage of rent	3.00%
Rent paid			$ 0.8	$ 0.8
Noncancelable Facility Lease Agreement \| Restricted Cash \| Letter of Credit \| 2019 Lease
Lessee Lease Description [Line Items]
Security deposit			1.6	1.6
Noncancelable Facility Lease Agreement \| Restricted Cash \| Letter of Credit \| 2021 Lease
Lessee Lease Description [Line Items]
Security deposit			$ 4.5	$ 4.5
Facility Sublease Agreement
Lessee Lease Description [Line Items]
Lease commencement date	Nov. 30, 2023