Optiong grant date.

No definition available.

Name:	epzm_OptionGrantDate
Namespace Prefix:	epzm_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

+ 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 (c)(1)(iii)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

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

- Definition

Net number of share options (or share units) granted during the period.

+ 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 (c)(1)(iv)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

+ Details

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

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
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- Details

Name:	us-gaap_PlanNameAxis=epzm_TwoThousandThirteenStockIncentivePlanMember
Namespace Prefix:
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Subsequent Events - Additional Information (Details) - $ / shares		12 Months Ended
	Apr. 01, 2022	Dec. 31, 2021	Mar. 31, 2022	Aug. 16, 2021
Subsequent Event [Line Items]
Weighted Average Exercise Price per Share, Exercisable			$ 14.14	$ 5.12
Common Stock [Member]
Subsequent Event [Line Items]
Aggregate number of stock granted to purchase		248,366
Subsequent Event [Member]
Subsequent Event [Line Items]
Grant date of option	Apr. 01, 2022
Subsequent Event [Member] \| Common Stock [Member]
Subsequent Event [Line Items]
Weighted Average Exercise Price per Share, Exercisable	$ 1.14
Subsequent Event [Member] \| 2013 Stock Incentive Plan [Member]
Subsequent Event [Line Items]
Aggregate number of stock granted to purchase	800,000,000