Number of contingent shares of equity interests issued or issuable to acquire entity.

No definition available.

Name:	kala_BusinessAcquisitionEquityInterestIssuedOrIssuableContingentNumberOfShares
Namespace Prefix:	kala_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of contingent milestone consideration in connection with acquisition.

+ References

No definition available.

+ Details

Name:	kala_BusinessCombinationContingentMilestoneConsiderationPayable
Namespace Prefix:	kala_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of contingent milestone consideration payable in cash in connection with acquisition.

+ References

No definition available.

+ Details

Name:	kala_BusinessCombinationContingentMilestoneConsiderationPayableInCash
Namespace Prefix:	kala_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of contingent milestone consideration payable in shares in connection with acquisition.

+ References

No definition available.

+ Details

Name:	kala_BusinessCombinationContingentMilestoneConsiderationPayableInShares
Namespace Prefix:	kala_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of cash cap for contingent cash consideration payable.

+ References

No definition available.

+ Details

Name:	kala_BusinessCombinationMinimumContingentCashConsiderationCashCap
Namespace Prefix:	kala_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Minimum percentage of Post-Closing Stock Consideration or any Contingent Stock Consideration resulting in to pay the portion of the Post-Closing Stock Consideration or any Contingent Stock Consideration in excess of the Share Cap in cash.

+ References

No definition available.

+ Details

Name:	kala_BusinessCombinationMinimumPostClosingStockAndContingentStockConsiderationPercentage
Namespace Prefix:	kala_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of upfront payment transferred in connection with acquisition.

+ References

No definition available.

+ Details

Name:	kala_BusinessCombinationUpfrontPayment
Namespace Prefix:	kala_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Number of shares of equity interests issued or issuable to acquire entity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479

+ Details

Name:	us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of equity interests of the acquirer, including instruments or interests issued or issuable in consideration for the business combination.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6613-128477

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 30
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6578-128477

+ Details

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

- Definition

Face amount or stated value per share of common stock.

+ 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(29))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_CommonStockParOrStatedValuePerShare
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of gain (loss) on termination of lease before expiration of lease term.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 40
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=123386189&loc=SL77918607-209975

+ Details

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

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

- Details

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

- Details

Name:	us-gaap_BusinessAcquisitionAxis=kala_CombangioIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	srt_StatementScenarioAxis=kala_FirstPatientDosedWithAnyProductInPhase2ClinicalTrialDosingMilestoneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=kala_FirstPatientDosedWithProductCandidateInPivotalClinicalTrialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=kala_BlaApprovalMilestoneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=kala_CommercializationMilestoneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=kala_NetSalesMilestonePaymentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

SUBSEQUENT EVENTS (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended
	Jan. 03, 2022	Nov. 15, 2021	Nov. 30, 2021	Sep. 30, 2021	Dec. 31, 2020
Subsequent Events
Common stock, par value				$ 0.001	$ 0.001
Subsequent Events
Subsequent Events
Termination of lease, amount			$ 2,000
Combangio, Inc \| Subsequent Events
Subsequent Events
Upfront payment		$ 5,000
Number of shares issuable	6,815,129	7,788,667
Common stock, par value		$ 0.001
Value of stock issuable		$ 16,123
Number of shares to be held back		973,538
Minimum percentage of Post-Closing Stock		19.90%
Amount of cash cap for contingent cash consideration payable		$ 2,500
Combangio, Inc \| Subsequent Events \| Maximum
Subsequent Events
Contingent milestone consideration		105,000
Combangio, Inc \| First Patient Dosed With Any Product in Phase 2 Clinical Trial, Dosing Milestone \| Subsequent Events
Subsequent Events
Contingent milestone consideration payable in cash		2,300
Contingent milestone consideration payable in shares		2,700
Combangio, Inc \| First Patient Dosed With Product Candidate in Pivotal Clinical Trial \| Subsequent Events
Subsequent Events
Contingent milestone consideration payable in cash		2,300
Contingent milestone consideration payable in shares		2,700
Combangio, Inc \| BLA Approval Milestone \| Subsequent Events
Subsequent Events
Contingent milestone consideration payable in cash		12,500
Contingent milestone consideration payable in shares		6,250
Combangio, Inc \| Commercialization Milestone \| Subsequent Events
Subsequent Events
Contingent milestone consideration payable in cash		17,500
Contingent milestone consideration payable in shares		8,750
Combangio, Inc \| Net Sales Milestone Payments \| Subsequent Events
Subsequent Events
Contingent milestone consideration payable in cash		$ 65,000