Revenue earned from sale of future royalties during the period from the leasing or otherwise lending to a third party the entity's rights or title to certain property

No definition available.

+ Details

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- Definition

Represents the period in arrears to receive royalty reports and payments related to sales of Kadcyla.

+ References

No definition available.

+ 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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- Definition

Revenue earned during the period from the leasing or otherwise lending to a third party the entity's rights or title to certain property. Royalty revenue is derived from a percentage or stated amount of sales proceeds or revenue generated by the third party using the entity's property. Examples of property from which royalties may be derived include patents and oil and mineral rights.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(e))
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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- Details

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- Details

Name:	us-gaap_CounterpartyNameAxis=imgn_RocheMember
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- Details

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- Details

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Collaborative Agreements - Roche (Details) - USD ($)	3 Months Ended		9 Months Ended
Collaborative Agreements - Roche (Details) - USD ($)	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Collaborative Agreements disclosures
Non-cash royalty revenue related to sale of future royalties	$ 7,380,000		$ 19,355,000
Royalties on net sales of Kadcyla		$ 5,099,000	$ 195,000	$ 13,890,000
Exclusive license \| Roche \| Development and Commercialization License \| Kadcyla
Collaborative Agreements disclosures
Period in arrears to receive royalty reports and payments related to sales of Kadcyla			1 month
Non-cash royalty revenue related to sale of future royalties			$ 19,400,000
Royalties on net sales of Kadcyla			$ 195,000	$ 13,900,000