The percentage of aggregate number of common shares reserved for future issuance.

No definition available.

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Namespace Prefix:	kala_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate number of common shares reserved for future issuance.

+ 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=6877327&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

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- 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

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Period Type:	duration

- Definition

Number of options outstanding, including both vested and non-vested options.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

+ Details

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

- Details

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Namespace Prefix:
Data Type:	na
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Period Type:

- Details

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- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
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- Details

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Data Type:	na
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- Details

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Balance Type:
Period Type:

- Details

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Data Type:	na
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- Details

Name:	us-gaap_AwardTypeAxis=kala_EmployeeStockPurchasePlanMember
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Stock-based Compensation - Narrative (Details) - shares	3 Months Ended	12 Months Ended
Stock-based Compensation - Narrative (Details) - shares	Mar. 31, 2020	Dec. 31, 2017	Dec. 31, 2019
Stock-based compensation
Common stock available for future grant	9,961,500		8,488,405
2017 Equity Incentive Plan
Stock-based compensation
Common stock available for future grant	138,513
2017 Equity Incentive Plan \| Maximum
Stock-based compensation
Common stock available for future grant	2,439,678
2017 Equity Incentive Plan \| Minimum
Stock-based compensation
Common stock available for future grant		3,573,766
Percentage of aggregate number of common shares reserved for future issuance (as a percent)		4.00%
2009 plan
Stock-based compensation
Common stock available for future grant	2,439,678		2,530,586
Number of shares outstanding	8,817,943		7,453,076
Employee and Non-Employee Stock Options
Stock-based compensation
Common stock available for future grant	709,500		705,500
Employee and Non-Employee Stock Options \| 2009 plan
Stock-based compensation
Options Expiry Term	10 years
Vesting Period	4 years
Performance Stock Options
Stock-based compensation
Number of shares outstanding	0
ESPP
Stock-based compensation
Common stock available for future grant	523,860		438,307